forked from itwanger/toBeBetterJavaer
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy patharray.html
More file actions
170 lines (157 loc) · 94.4 KB
/
array.html
File metadata and controls
170 lines (157 loc) · 94.4 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
<!doctype html>
<html lang="zh-CN" data-theme="light">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width,initial-scale=1" />
<meta name="generator" content="VuePress 2.0.0-beta.67" />
<meta name="theme" content="VuePress Theme Hope" />
<meta name="keywords" content="Java, 数组, 创建数组, 初始化数组, 数组操作"><meta property="og:url" content="https://javabetter.cn/array/array.html"><meta property="og:site_name" content="二哥的Java进阶之路"><meta property="og:title" content="掌握Java数组：一个非常特殊的对象"><meta property="og:description" content="本文详细介绍了Java数组，包括数组的基本概念、创建方法、初始化方法以及常用操作。学习本文内容，您将掌握Java数组的定义、如何创建和初始化数组，以及如何进行数组元素的添加、删除、查询等操作，为您的Java编程之旅打下坚实基础。"><meta property="og:type" content="article"><meta property="og:locale" content="zh-CN"><meta property="og:updated_time" content="2024-04-13T02:41:36.000Z"><meta property="article:author" content="沉默王二"><meta property="article:tag" content="数组&字符串"><meta property="article:modified_time" content="2024-04-13T02:41:36.000Z"><script type="application/ld+json">{"@context":"https://schema.org","@type":"Article","headline":"掌握Java数组：一个非常特殊的对象","image":[""],"dateModified":"2024-04-13T02:41:36.000Z","author":[{"@type":"Person","name":"沉默王二","url":"/about-the-author/"}]}</script><meta name="robots" content="all"><meta name="author" content="沉默王二"><meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate"><meta http-equiv="Pragma" content="no-cache"><meta http-equiv="Expires" content="0"><meta name="apple-mobile-web-app-capable" content="yes"><script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?5230ac143650bf5eb3c14f3fb9b1d3ec";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script><script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?59aa453e7e706422c636c079fc1cb031";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script><link rel="stylesheet" href="//at.alicdn.com/t/font_3180624_7cy10l7jqqh.css"><link rel="manifest" href="/manifest.webmanifest" crossorigin="use-credentials"><meta name="theme-color" content="#46bd87"><meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, viewport-fit=cover"><link rel="icon" href="https://cdn.tobebetterjavaer.com/tobebetterjavaer/images/favicon.ico"><link rel="icon" href="/assets/icon/chrome-mask-512.png" type="image/png" sizes="512x512"><link rel="icon" href="/assets/icon/chrome-mask-192.png" type="image/png" sizes="192x192"><link rel="icon" href="/assets/icon/chrome-512.png" type="image/png" sizes="512x512"><link rel="icon" href="/assets/icon/chrome-192.png" type="image/png" sizes="192x192"><link rel="apple-touch-icon" href="/assets/icon/apple-icon-152.png"><meta name="apple-mobile-web-app-status-bar-style" content="black"><meta name="msapplication-TileImage" content="/assets/icon/ms-icon-144.png"><meta name="msapplication-TileColor" content="#ffffff"><title>掌握Java数组：一个非常特殊的对象 | 二哥的Java进阶之路</title><meta name="description" content="本文详细介绍了Java数组，包括数组的基本概念、创建方法、初始化方法以及常用操作。学习本文内容，您将掌握Java数组的定义、如何创建和初始化数组，以及如何进行数组元素的添加、删除、查询等操作，为您的Java编程之旅打下坚实基础。">
<style>
:root {
--bg-color: #fff;
}
html[data-theme="dark"] {
--bg-color: #1d1e1f;
}
html,
body {
background: var(--bg-color);
}
</style>
<script>
const userMode = localStorage.getItem("vuepress-theme-hope-scheme");
const systemDarkMode =
window.matchMedia &&
window.matchMedia("(prefers-color-scheme: dark)").matches;
if (userMode === "dark" || (userMode !== "light" && systemDarkMode)) {
document.documentElement.setAttribute("data-theme", "dark");
}
</script>
<link rel="preload" href="/assets/style-ebd0477e.css" as="style"><link rel="stylesheet" href="/assets/style-ebd0477e.css">
<link rel="modulepreload" href="/assets/app-b1913f48.js"><link rel="modulepreload" href="/assets/array.html-7a961a1a.js"><link rel="modulepreload" href="/assets/plugin-vue_export-helper-c27b6911.js"><link rel="modulepreload" href="/assets/array.html-7199902d.js">
</head>
<body>
<div id="app"><!--[--><!--[--><!--[--><span tabindex="-1"></span><a href="#main-content" class="vp-skip-link sr-only">跳至主要內容</a><!--]--><div class="theme-container has-toc"><!--[--><header id="navbar" class="vp-navbar"><div class="vp-navbar-start"><button type="button" class="vp-toggle-sidebar-button" title="Toggle Sidebar"><span class="icon"></span></button><!--[--><!----><!--]--><!--[--><a class="vp-link vp-brand" href="/"><img class="vp-nav-logo" src="https://cdn.tobebetterjavaer.com/tobebetterjavaer/images/logo-02.png" alt="二哥的Java进阶之路"><!----><span class="vp-site-name hide-in-pad">二哥的Java进阶之路</span></a><!--]--><!--[--><!----><!--]--></div><div class="vp-navbar-center"><!--[--><!----><!--]--><!--[--><nav class="vp-nav-links"><div class="nav-item hide-in-mobile"><a class="vp-link nav-link" href="/blog.html"><span class="font-icon icon iconfont icon-gaishu" style=""></span>博客<!----></a></div><div class="nav-item hide-in-mobile"><a class="vp-link nav-link" href="/home.html"><span class="font-icon icon iconfont icon-lujing" style=""></span>进阶之路<!----></a></div><div class="nav-item hide-in-mobile"><a class="vp-link nav-link" href="/zhishixingqiu/"><span class="font-icon icon iconfont icon-Artboard" style=""></span>知识星球<!----></a></div><div class="nav-item hide-in-mobile"><a class="vp-link nav-link" href="/xuexiluxian/"><span class="font-icon icon iconfont icon-luxian" style=""></span>学习路线<!----></a></div><div class="nav-item hide-in-mobile"><div class="dropdown-wrapper"><button type="button" class="dropdown-title" aria-label="珍藏资源"><span class="title"><span class="font-icon icon iconfont icon-youzhi" style=""></span>珍藏资源</span><span class="arrow"></span><ul class="nav-dropdown"><li class="dropdown-item"><a class="vp-link nav-link" href="/pdf/"><span class="font-icon icon iconfont icon-java" style=""></span>PDF下载<!----></a></li><li class="dropdown-item"><a class="vp-link nav-link" href="/sidebar/sanfene/nixi.html"><span class="font-icon icon iconfont icon-zhunbei" style=""></span>面渣逆袭<!----></a></li><li class="dropdown-item"><a class="vp-link nav-link" href="/nice-article/itmind/"><span class="font-icon icon iconfont icon-zhongyaotishi" style=""></span>破解合集<!----></a></li></ul></button></div></div><div class="nav-item hide-in-mobile"><a href="https://space.bilibili.com/513340480" rel="noopener noreferrer" target="_blank" aria-label="B站视频" class="nav-link"><span class="font-icon icon iconfont icon-bzhan" style=""></span>B站视频<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div></nav><!--]--><!--[--><!----><!--]--></div><div class="vp-navbar-end"><!--[--><!----><!--]--><!--[--><!----><div class="nav-item vp-repo"><a class="vp-repo-link" href="https://github.com/itwanger/toBeBetterJavaer" target="_blank" rel="noopener noreferrer" aria-label="GitHub"><svg xmlns="http://www.w3.org/2000/svg" class="icon github-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="github icon" style="width:1.25rem;height:1.25rem;vertical-align:middle;"><path d="M511.957 21.333C241.024 21.333 21.333 240.981 21.333 512c0 216.832 140.544 400.725 335.574 465.664 24.49 4.395 32.256-10.07 32.256-23.083 0-11.69.256-44.245 0-85.205-136.448 29.61-164.736-64.64-164.736-64.64-22.315-56.704-54.4-71.765-54.4-71.765-44.587-30.464 3.285-29.824 3.285-29.824 49.195 3.413 75.179 50.517 75.179 50.517 43.776 75.008 114.816 53.333 142.762 40.79 4.523-31.66 17.152-53.377 31.19-65.537-108.971-12.458-223.488-54.485-223.488-242.602 0-53.547 19.114-97.323 50.517-131.67-5.035-12.33-21.93-62.293 4.779-129.834 0 0 41.258-13.184 134.912 50.346a469.803 469.803 0 0 1 122.88-16.554c41.642.213 83.626 5.632 122.88 16.554 93.653-63.488 134.784-50.346 134.784-50.346 26.752 67.541 9.898 117.504 4.864 129.834 31.402 34.347 50.474 78.123 50.474 131.67 0 188.586-114.73 230.016-224.042 242.09 17.578 15.232 33.578 44.672 33.578 90.454v135.85c0 13.142 7.936 27.606 32.854 22.87C862.25 912.597 1002.667 728.747 1002.667 512c0-271.019-219.648-490.667-490.71-490.667z"></path></svg></a></div><div class="nav-item hide-in-mobile"><button type="button" class="outlook-button" tabindex="-1" aria-hidden="true"><svg xmlns="http://www.w3.org/2000/svg" class="icon outlook-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="outlook icon"><path d="M224 800c0 9.6 3.2 44.8 6.4 54.4 6.4 48-48 76.8-48 76.8s80 41.6 147.2 0 134.4-134.4 38.4-195.2c-22.4-12.8-41.6-19.2-57.6-19.2C259.2 716.8 227.2 761.6 224 800zM560 675.2l-32 51.2c-51.2 51.2-83.2 32-83.2 32 25.6 67.2 0 112-12.8 128 25.6 6.4 51.2 9.6 80 9.6 54.4 0 102.4-9.6 150.4-32l0 0c3.2 0 3.2-3.2 3.2-3.2 22.4-16 12.8-35.2 6.4-44.8-9.6-12.8-12.8-25.6-12.8-41.6 0-54.4 60.8-99.2 137.6-99.2 6.4 0 12.8 0 22.4 0 12.8 0 38.4 9.6 48-25.6 0-3.2 0-3.2 3.2-6.4 0-3.2 3.2-6.4 3.2-6.4 6.4-16 6.4-16 6.4-19.2 9.6-35.2 16-73.6 16-115.2 0-105.6-41.6-198.4-108.8-268.8C704 396.8 560 675.2 560 675.2zM224 419.2c0-28.8 22.4-51.2 51.2-51.2 28.8 0 51.2 22.4 51.2 51.2 0 28.8-22.4 51.2-51.2 51.2C246.4 470.4 224 448 224 419.2zM320 284.8c0-22.4 19.2-41.6 41.6-41.6 22.4 0 41.6 19.2 41.6 41.6 0 22.4-19.2 41.6-41.6 41.6C339.2 326.4 320 307.2 320 284.8zM457.6 208c0-12.8 12.8-25.6 25.6-25.6 12.8 0 25.6 12.8 25.6 25.6 0 12.8-12.8 25.6-25.6 25.6C470.4 233.6 457.6 220.8 457.6 208zM128 505.6C128 592 153.6 672 201.6 736c28.8-60.8 112-60.8 124.8-60.8-16-51.2 16-99.2 16-99.2l316.8-422.4c-48-19.2-99.2-32-150.4-32C297.6 118.4 128 291.2 128 505.6zM764.8 86.4c-22.4 19.2-390.4 518.4-390.4 518.4-22.4 28.8-12.8 76.8 22.4 99.2l9.6 6.4c35.2 22.4 80 12.8 99.2-25.6 0 0 6.4-12.8 9.6-19.2 54.4-105.6 275.2-524.8 288-553.6 6.4-19.2-3.2-32-19.2-32C777.6 76.8 771.2 80 764.8 86.4z"></path></svg><div class="outlook-dropdown"><!----></div></button></div><!--[--><div id="docsearch-container" style="display:none;"></div><div><button type="button" class="DocSearch DocSearch-Button" aria-label="搜索文档"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">搜索文档</span></span><span class="DocSearch-Button-Keys"><kbd class="DocSearch-Button-Key"><svg width="15" height="15" class="DocSearch-Control-Key-Icon"><path d="M4.505 4.496h2M5.505 5.496v5M8.216 4.496l.055 5.993M10 7.5c.333.333.5.667.5 1v2M12.326 4.5v5.996M8.384 4.496c1.674 0 2.116 0 2.116 1.5s-.442 1.5-2.116 1.5M3.205 9.303c-.09.448-.277 1.21-1.241 1.203C1 10.5.5 9.513.5 8V7c0-1.57.5-2.5 1.464-2.494.964.006 1.134.598 1.24 1.342M12.553 10.5h1.953" stroke-width="1.2" stroke="currentColor" fill="none" stroke-linecap="square"></path></svg></kbd><kbd class="DocSearch-Button-Key">K</kbd></span></button></div><!--]--><!--]--><!--[--><!----><!--]--><button type="button" class="vp-toggle-navbar-button" aria-label="Toggle Navbar" aria-expanded="false" aria-controls="nav-screen"><span><span class="vp-top"></span><span class="vp-middle"></span><span class="vp-bottom"></span></span></button></div></header><!----><!--]--><!----><div class="toggle-sidebar-wrapper"><span class="arrow start"></span></div><aside id="sidebar" class="vp-sidebar"><!--[--><!----><!--]--><ul class="vp-sidebar-links"><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/home.html"><!---->一、前言<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable active" type="button"><!----><span class="vp-sidebar-title">二、Java基础</span><span class="vp-arrow down"></span></button><ul class="vp-sidebar-links"><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.1 Java概述及环境配置</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.2 Java语法基础</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable active" type="button"><!----><span class="vp-sidebar-title">2.3 数组&字符串</span><span class="vp-arrow down"></span></button><ul class="vp-sidebar-links"><li><!--[--><a class="vp-link nav-link active vp-sidebar-link vp-sidebar-page active" href="/array/array.html"><!---->数组<!----></a><ul class="vp-sidebar-sub-headers"><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组的声明与初始化"><!---->数组的声明与初始化<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组的常用操作"><!---->数组的常用操作<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#可变参数与数组"><!---->可变参数与数组<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组与-list"><!---->数组与 List<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组的排序与查找"><!---->数组的排序与查找<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组的复制"><!---->数组的复制<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#数组越界"><!---->数组越界<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/array/array.html#小结"><!---->小结<!----></a><ul class="vp-sidebar-sub-headers"></ul></li></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/array/double-array.html"><!---->二维数组<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/array/print.html"><!---->打印数组<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/string-source.html"><!---->字符串源码解读<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/immutable.html"><!---->字符串为什么不可变<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/constant-pool.html"><!---->字符串常量池<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/intern.html"><!---->String.intern详解<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/builder-buffer.html"><!---->StringBuilder和StringBuffer<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/equals.html"><!---->如何判断字符串相等<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/join.html"><!---->如何拼接字符串<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/string/split.html"><!---->如何拆分字符串<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.4 面向对象编程</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.5 集合框架（容器）</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.6 Java IO</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.7 异常处理</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.8 常用工具类</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><a class="vp-link nav-link vp-sidebar-title" href="/java8/"><!---->2.9 Java新特性<!----></a><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.10 网络编程</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.11 NIO</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.12 Java重要知识点</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.13 并发编程</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.14 JVM</span><span class="vp-arrow end"></span></button><!----></section></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">三、Java进阶</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">四、MySQL</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">五、Redis</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">六、计算机基础</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">七、求职面试</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">八、学习建议</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">九、知识库搭建</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">十、联系作者</span><span class="vp-arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main id="main-content" class="vp-page"><!--[--><!----><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->掌握Java数组：一个非常特殊的对象</h1><div class="page-info"><span class="page-author-info" aria-label="作者🖊" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon author-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="author icon"><path d="M649.6 633.6c86.4-48 147.2-144 147.2-249.6 0-160-128-288-288-288s-288 128-288 288c0 108.8 57.6 201.6 147.2 249.6-121.6 48-214.4 153.6-240 288-3.2 9.6 0 19.2 6.4 25.6 3.2 9.6 12.8 12.8 22.4 12.8h704c9.6 0 19.2-3.2 25.6-12.8 6.4-6.4 9.6-16 6.4-25.6-25.6-134.4-121.6-240-243.2-288z"></path></svg><span><a class="page-author-item" href="/about-the-author/" target="_blank" rel="noopener noreferrer">沉默王二</a></span><span property="author" content="沉默王二"></span></span><!----><span class="page-date-info" aria-label="写作日期📅" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span><!----></span><meta property="datePublished" content="2021-10-22T07:22:10.000Z"></span><span class="page-category-info" aria-label="分类🌈" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon category-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="category icon"><path d="M148.41 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H148.41c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.311-40.31zM147.556 553.478H429.73c22.263 0 40.311 18.048 40.311 40.31v282.176c0 22.263-18.048 40.312-40.31 40.312H147.555c-22.263 0-40.311-18.049-40.311-40.312V593.79c0-22.263 18.048-40.311 40.31-40.311zM593.927 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H593.927c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.31-40.31zM730.22 920.502H623.926c-40.925 0-74.22-33.388-74.22-74.425V623.992c0-41.038 33.387-74.424 74.425-74.424h222.085c41.038 0 74.424 33.226 74.424 74.067v114.233c0 10.244-8.304 18.548-18.547 18.548s-18.548-8.304-18.548-18.548V623.635c0-20.388-16.746-36.974-37.33-36.974H624.13c-20.585 0-37.331 16.747-37.331 37.33v222.086c0 20.585 16.654 37.331 37.126 37.331H730.22c10.243 0 18.547 8.304 18.547 18.547 0 10.244-8.304 18.547-18.547 18.547z"></path></svg><!--[--><span class="page-category-item category0 clickable" role="navigation">Java核心</span><!--]--><meta property="articleSection" content="Java核心"></span><span class="page-tag-info" aria-label="标签🏷" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon tag-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="tag icon"><path d="M939.902 458.563L910.17 144.567c-1.507-16.272-14.465-29.13-30.737-30.737L565.438 84.098h-.402c-3.215 0-5.726 1.005-7.634 2.913l-470.39 470.39a10.004 10.004 0 000 14.164l365.423 365.424c1.909 1.908 4.42 2.913 7.132 2.913s5.223-1.005 7.132-2.913l470.39-470.39c2.01-2.11 3.014-5.023 2.813-8.036zm-240.067-72.121c-35.458 0-64.286-28.828-64.286-64.286s28.828-64.285 64.286-64.285 64.286 28.828 64.286 64.285-28.829 64.286-64.286 64.286z"></path></svg><!--[--><span class="page-tag-item tag5 clickable" role="navigation">数组&字符串</span><!--]--><meta property="keywords" content="数组&字符串"></span><span class="page-word-info" aria-label="字数🔠" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon word-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="word icon"><path d="M518.217 432.64V73.143A73.143 73.143 0 01603.43 1.097a512 512 0 01419.474 419.474 73.143 73.143 0 01-72.046 85.212H591.36a73.143 73.143 0 01-73.143-73.143z"></path><path d="M493.714 566.857h340.297a73.143 73.143 0 0173.143 85.577A457.143 457.143 0 11371.566 117.76a73.143 73.143 0 0185.577 73.143v339.383a36.571 36.571 0 0036.571 36.571z"></path></svg><span>约 3241 字</span><meta property="wordCount" content="3241"></span><span class="page-reading-time-info" aria-label="阅读时间⌛" data-balloon-pos="down"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>大约 11 分钟</span><meta property="timeRequired" content="PT11M"></span></div><hr></div><div class="toc-place-holder"><aside id="toc"><!--[--><!----><!--]--><div class="toc-header">此页内容<button type="button" class="print-button" title="打印"><svg xmlns="http://www.w3.org/2000/svg" class="icon print-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="print icon"><path d="M819.2 364.8h-44.8V128c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v236.8h-44.8C145.067 364.8 96 413.867 96 473.6v192c0 59.733 49.067 108.8 108.8 108.8h44.8V896c0 17.067 14.933 32 32 32h460.8c17.067 0 32-14.933 32-32V774.4h44.8c59.733 0 108.8-49.067 108.8-108.8v-192c0-59.733-49.067-108.8-108.8-108.8zM313.6 160h396.8v204.8H313.6V160zm396.8 704H313.6V620.8h396.8V864zM864 665.6c0 25.6-19.2 44.8-44.8 44.8h-44.8V588.8c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v121.6h-44.8c-25.6 0-44.8-19.2-44.8-44.8v-192c0-25.6 19.2-44.8 44.8-44.8h614.4c25.6 0 44.8 19.2 44.8 44.8v192z"></path></svg></button></div><div class="toc-wrapper"><ul class="toc-list"><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组的声明与初始化">数组的声明与初始化</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组的常用操作">数组的常用操作</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#可变参数与数组">可变参数与数组</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组与-list">数组与 List</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组的排序与查找">数组的排序与查找</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组的复制">数组的复制</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#数组越界">数组越界</a></li><!----><!--]--><!--[--><li class="toc-item"><a class="vp-link toc-link level3" href="/#小结">小结</a></li><!----><!--]--></ul><div class="toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!----><div class="theme-hope-content"><h1 id="_4-1-数组" tabindex="-1"><a class="header-anchor" href="#_4-1-数组" aria-hidden="true">#</a> 4.1 数组</h1><p>“二哥，我看你公众号的一篇文章里提到，<a href="https://javabetter.cn/collection/arraylist.html" target="_blank" rel="noopener noreferrer">ArrayList<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a> 的内部是用数组实现的，我就对数组非常感兴趣，想深入地了解一下，今天终于到这个环节了，好期待呀！”三妹的语气里显得很兴奋。</p><p>“的确是的，看 ArrayList 的源码就一清二楚了。”我一边说，一边打开 Intellij IDEA，并找到了 ArrayList 的源码。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token doc-comment comment">/**
* The array buffer into which the elements of the ArrayList are stored.
* The capacity of the ArrayList is the length of this array buffer. Any
* empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
* will be expanded to DEFAULT_CAPACITY when the first element is added.
*/</span>
<span class="token keyword">transient</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> elementData<span class="token punctuation">;</span> <span class="token comment">// non-private to simplify nested class access</span>
<span class="token doc-comment comment">/**
* The size of the ArrayList (the number of elements it contains).
*
* <span class="token keyword">@serial</span>
*/</span>
<span class="token keyword">private</span> <span class="token keyword">int</span> size<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>“瞧见没？<code>Object[] elementData</code> 就是数组。”我指着显示屏上这串代码继续说。</p><p>数组是一个对象，它包含了一组固定数量的元素，并且这些元素的类型是相同的。数组会按照索引的方式将元素放在指定的位置上，意味着我们可以通过索引来访问这些元素。在 Java 中，索引是从 0 开始的。</p><p>“哥，能说一下为什么索引从 0 开始吗？”三妹突然对这个话题很感兴趣。</p><p>“哦，Java 是基于 C/C++ 语言实现的，而 C 语言的下标是从 0 开始的，所以 Java 就继承了这个良好的传统习惯（<em>我瞎编的</em>）。C语言有一个很重要概念，叫做指针，它实际上是一个偏移量，距离开始位置的偏移量，第一个元素就在开始的位置，它的偏移量就为 0，所以索引就为 0。”此刻，我很自信。</p><p>“此外，还有另外一种说法。早期的计算机资源比较匮乏，0 作为起始下标相比较于 1 作为起始下标，编译的效率更高。”</p><p>“哦。”三妹意味深长地点了点头。</p><p>我们可以将数组理解为一个个整齐排列的单元格，每个单元格里面存放着一个元素。</p><p>比如说下图中的数组，值为[a,b,c,a,b,c,b,b]，下标依次为 0、1、2、3、4、5、6、7。</p><figure><img src="https://cdn.tobebetterjavaer.com/stutymore/array-20231213153711.png" alt="" tabindex="0" loading="lazy"><figcaption></figcaption></figure><p>数组元素的类型可以是基本数据类型（比如说 int、double），也可以是引用数据类型（比如说 String），包括自定义类型。</p><h3 id="数组的声明与初始化" tabindex="-1"><a class="header-anchor" href="#数组的声明与初始化" aria-hidden="true">#</a> 数组的声明与初始化</h3><p>数组的声明方式分两种。</p><p>先来看第一种：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>再来看第二种：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>不同之处就在于中括号的位置，是跟在类型关键字的后面，还是跟在变量的名称的后面。前一种的使用频率更高一些，像 ArrayList 的源码中就用了第一种方式。</p><p>同样的，数组的初始化方式也有多种，最常见的是：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>看到没？上面这行代码中使用了 new 关键字，这就意味着数组的确是一个对象，只有对象的创建才会用到 new 关键字，<a href="https://javabetter.cn/basic-grammar/basic-data-type.html" target="_blank" rel="noopener noreferrer">基本数据类型<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>是不用的（基本数据的包装类型是可以 new 的，包装类型就是对象）。然后，我们需要在方括号中指定数组的长度。</p><p>这时候，数组中的每个元素都会被初始化为默认值，int 类型的就为 0，Object 类型的就为 null。 不同数据类型的默认值不同，可以参照<a href="https://javabetter.cn/basic-grammar/basic-data-type.html" target="_blank" rel="noopener noreferrer">之前的文章<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>。</p><p>另外，还可以使用大括号的方式，直接初始化数组中的元素：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>这时候，数组的元素分别是 1、2、3、4、5，索引依次是 0、1、2、3、4，长度是 5。</p><h3 id="数组的常用操作" tabindex="-1"><a class="header-anchor" href="#数组的常用操作" aria-hidden="true">#</a> 数组的常用操作</h3><p>“哥，怎么访问数组呢？”三妹及时地插话到。</p><p>前面提到过，可以通过索引来访问数组的元素，就像下面这样：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code>anArray<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>变量名，加上中括号，加上元素的索引，就可以访问到数组，通过“=”操作符可以对元素进行赋值。</p><p>如果索引的值超出了数组的界限，就会抛出 <code>ArrayIndexOutOfBoundException</code>。由于数组的索引是从 0 开始，所以最大索引为 <code>length - 1</code>，不要使用超出这个范围内的索引访问数组，否则就会抛出数组越界的异常了。</p><p>比如说你声明了一个大小为 10 的数组，你用索引 10 来访问数组，就会抛出这个异常。因为数组的索引是从 0 开始的，所以数组的最后一个元素的索引是 <code>length - 1</code>，也就是 9。</p><p>当数组的元素非常多的时候，逐个访问数组就太辛苦了，所以需要通过遍历的方式。</p><p>第一种，使用 for 循环：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> anOtherArray<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>anOtherArray<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>通过 length 属性获取到数组的长度，然后从 0 开始遍历，就得到了数组的所有元素。</p><p>第二种，使用 for-each 循环：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> anOtherArray<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>element<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>如果不需要关心索引的话（意味着不需要修改数组的某个元素），使用 for-each 遍历更简洁一些。当然，也可以使用 while 和 do-while 循环。</p><h3 id="可变参数与数组" tabindex="-1"><a class="header-anchor" href="#可变参数与数组" aria-hidden="true">#</a> 可变参数与数组</h3><p>在 Java 中，可变参数用于将任意数量的参数传递给方法，来看 <code>varargsMethod()</code> 方法：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">void</span> <span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> varargs<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>该方法可以接收任意数量的字符串参数，可以是 0 个或者 N 个，本质上，可变参数就是通过数组实现的。为了证明这一点，我们可以看一下反编译一后的字节码：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">VarargsDemo</span>
<span class="token punctuation">{</span>
<span class="token keyword">public</span> <span class="token class-name">VarargsDemo</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token punctuation">}</span>
<span class="token keyword">transient</span> <span class="token keyword">void</span> <span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token class-name">String</span> as<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token punctuation">{</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>所以，我们其实可以直接将数组作为参数传递给该方法：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">VarargsDemo</span> demo <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">VarargsDemo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">"沉默王二"</span><span class="token punctuation">,</span> <span class="token string">"一枚有趣的程序员"</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
demo<span class="token punctuation">.</span><span class="token function">varargsMethod</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>也可以直接传递多个字符串，通过逗号隔开的方式：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code>demo<span class="token punctuation">.</span><span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token string">"沉默王二"</span><span class="token punctuation">,</span> <span class="token string">"一枚有趣的程序员"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h3 id="数组与-list" tabindex="-1"><a class="header-anchor" href="#数组与-list" aria-hidden="true">#</a> 数组与 List</h3><p>在 Java 中，数组与 List 关系非常密切。List 封装了很多常用的方法，方便我们对集合进行一些操作，而如果直接操作数组的话，有很多不便，因为数组本身没有提供这些封装好的操作，所以有时候我们需要把数组转成 List。</p><blockquote><p>List 会在<a href="https://javabetter.cn/collection/arraylist.html" target="_blank" rel="noopener noreferrer">集合框架<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>一节详细介绍，这里先来个开胃菜，方便大家回头过来复盘。</p></blockquote><p>“怎么转呢？”三妹问到。</p><p>最原始的方式，就是通过遍历数组的方式，一个个将数组添加到 List 中。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Integer</span><span class="token punctuation">></span></span> aList <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> anArray<span class="token punctuation">)</span> <span class="token punctuation">{</span>
aList<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>element<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>更优雅的方式是通过 <a href="https://javabetter.cn/common-tool/arrays.html" target="_blank" rel="noopener noreferrer">Arrays 类<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>（戳链接了解详情）的 <code>asList()</code> 方法：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Integer</span><span class="token punctuation">></span></span> aList <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>不过需要注意的是，Arrays.asList 的参数需要是 Integer 数组，而 anArray 目前是 int 类型。</p><p>可以这样写：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Integer</span><span class="token punctuation">></span></span> aList1 <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>或者换另外一种方式。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Integer</span><span class="token punctuation">></span></span> aList <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">stream</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">boxed</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">collect</span><span class="token punctuation">(</span><span class="token class-name">Collectors</span><span class="token punctuation">.</span><span class="token function">toList</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>这又涉及到了 <a href="https://javabetter.cn/java8/stream.html" target="_blank" rel="noopener noreferrer">Java 流<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>的知识，戳链接了解。</p><p>还有一个需要注意的是，Arrays.asList 方法返回的 ArrayList 并不是 <code>java.util.ArrayList</code>，它其实是 Arrays 类的一个内部类：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">E</span><span class="token punctuation">></span></span> <span class="token keyword">extends</span> <span class="token class-name">AbstractList</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">E</span><span class="token punctuation">></span></span>
<span class="token keyword">implements</span> <span class="token class-name">RandomAccess</span><span class="token punctuation">,</span> <span class="token class-name"><span class="token namespace">java<span class="token punctuation">.</span>io<span class="token punctuation">.</span></span>Serializable</span><span class="token punctuation">{</span><span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>如果需要添加元素或者删除元素的话，需要把它转成 <code>java.util.ArrayList</code>。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Java 8 新增了 <a href="https://javabetter.cn/java8/stream.html" target="_blank" rel="noopener noreferrer">Stream 流<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>的概念，这就意味着我们也可以将数组转成 Stream 进行操作。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">"沉默王二"</span><span class="token punctuation">,</span> <span class="token string">"一枚有趣的程序员"</span><span class="token punctuation">,</span> <span class="token string">"好好珍重他"</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Stream</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">></span></span> aStream <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">stream</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="数组的排序与查找" tabindex="-1"><a class="header-anchor" href="#数组的排序与查找" aria-hidden="true">#</a> 数组的排序与查找</h3><p>如果想对数组进行排序的话，可以使用 Arrays 类提供的 <code>sort()</code> 方法。</p><ul><li>基本数据类型按照升序排列</li><li>实现了 Comparable 接口的对象按照 <code>compareTo()</code> 的排序</li></ul><p>来看第一个例子：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>排序后的结果如下所示：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">]</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>来看第二个例子：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> yetAnotherArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">"A"</span><span class="token punctuation">,</span> <span class="token string">"E"</span><span class="token punctuation">,</span> <span class="token string">"Z"</span><span class="token punctuation">,</span> <span class="token string">"B"</span><span class="token punctuation">,</span> <span class="token string">"C"</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>yetAnotherArray<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span>
<span class="token class-name">Comparator</span><span class="token punctuation">.</span><span class="token function">comparing</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token operator">::</span><span class="token function">toString</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">reversed</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>只对 1-3 位置上的元素进行反序，所以结果如下所示：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>[A, Z, E, B, C]
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>有时候，我们需要从数组中查找某个具体的元素，最直接的方式就是通过遍历的方式：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> anArray<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>anArray<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"找到了 "</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">break</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>上例中从数组中查询元素 4，找到后通过 break 关键字退出循环。</p><p>如果数组提前进行了排序，就可以使用二分查找法，这样效率就会更高一些。<code>Arrays.binarySearch()</code> 方法可供我们使用，它需要传递一个数组，和要查找的元素。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">int</span> index <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">binarySearch</span><span class="token punctuation">(</span>anArray<span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>“除了一维数组，还有<a href="https://javabetter.cn/array/double-array.html" target="_blank" rel="noopener noreferrer">二维数组<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>，三妹你可以去研究下，比如说用二维数组打印一下杨辉三角，我们下一节会讲。”</p><h3 id="数组的复制" tabindex="-1"><a class="header-anchor" href="#数组的复制" aria-hidden="true">#</a> 数组的复制</h3><p>有时候我们需要将一个数组的值复制到另外一个数组当中，那就会涉及到数组复制的知识点。</p><p>在 <a href="https://javabetter.cn/string/string-source.html" target="_blank" rel="noopener noreferrer">String 类<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>（讲完数组就会讲）中其实会经常遇到数组复制，比如说 <code>substring()</code> 方法。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token class-name">String</span> <span class="token function">substring</span><span class="token punctuation">(</span><span class="token keyword">int</span> beginIndex<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token punctuation">(</span>beginIndex <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token keyword">this</span> <span class="token operator">:</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">(</span>value<span class="token punctuation">,</span> beginIndex<span class="token punctuation">,</span> subLen<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>注意其中的 <code>new String()</code>，它会返回一个新的字符串，这个字符串的值就是原字符串的一部分，这个过程就涉及到了数组的复制。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token class-name">String</span><span class="token punctuation">(</span><span class="token keyword">char</span> value<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token keyword">int</span> offset<span class="token punctuation">,</span> <span class="token keyword">int</span> count<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>value <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">copyOfRange</span><span class="token punctuation">(</span>value<span class="token punctuation">,</span> offset<span class="token punctuation">,</span> offset<span class="token operator">+</span>count<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>其中的 <code>Arrays.copyOfRange()</code> 方法就是用来复制数组的，我们在讲 <a href="https://javabetter.cn/common-tool/arrays.html#_2-copyofrange" target="_blank" rel="noopener noreferrer">Arrays 类<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>的时候就会讲到。</p><p>它底层调用的是 <code>System.arraycopy()</code> 方法，这个方法是一个 <a href="https://javabetter.cn/oo/native-method.html" target="_blank" rel="noopener noreferrer">native 方法<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>，它是用 C/C++ 实现的，效率非常高。</p><figure><img src="https://cdn.tobebetterjavaer.com/stutymore/array-20231213160102.png" alt="" tabindex="0" loading="lazy"><figcaption></figcaption></figure><p>System.arraycopy 方法的定义如下所示：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">native</span> <span class="token keyword">void</span> <span class="token function">arraycopy</span><span class="token punctuation">(</span><span class="token class-name">Object</span> src<span class="token punctuation">,</span> <span class="token keyword">int</span> srcPos<span class="token punctuation">,</span>
<span class="token class-name">Object</span> dest<span class="token punctuation">,</span> <span class="token keyword">int</span> destPos<span class="token punctuation">,</span>
<span class="token keyword">int</span> length<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>用法如下所示：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> array1 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> array2 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token comment">// 创建一个新数组，长度为两个数组长度之和</span>
<span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> mergedArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span>array1<span class="token punctuation">.</span>length <span class="token operator">+</span> array2<span class="token punctuation">.</span>length<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token comment">// 复制第一个数组到新数组</span>
<span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">arraycopy</span><span class="token punctuation">(</span>array1<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> mergedArray<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> array1<span class="token punctuation">.</span>length<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span>mergedArray<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 复制第二个数组到新数组</span>
<span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">arraycopy</span><span class="token punctuation">(</span>array2<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> mergedArray<span class="token punctuation">,</span> array1<span class="token punctuation">.</span>length<span class="token punctuation">,</span> array2<span class="token punctuation">.</span>length<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span>mergedArray<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>输出结果如下所示：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">]</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>当然了，我们也可以使用循环来完成数组的复制：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> array1 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> array2 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token comment">// 创建一个新数组，长度为两个数组长度之和</span>
<span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> mergedArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span>array1<span class="token punctuation">.</span>length <span class="token operator">+</span> array2<span class="token punctuation">.</span>length<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token comment">// 复制第一个数组到新数组</span>
<span class="token keyword">int</span> index <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> array1<span class="token punctuation">)</span> <span class="token punctuation">{</span>
mergedArray<span class="token punctuation">[</span>index<span class="token operator">++</span><span class="token punctuation">]</span> <span class="token operator">=</span> element<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// 复制第二个数组到新数组</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> array2<span class="token punctuation">)</span> <span class="token punctuation">{</span>
mergedArray<span class="token punctuation">[</span>index<span class="token operator">++</span><span class="token punctuation">]</span> <span class="token operator">=</span> element<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>很简单，很好理解，相信三妹你也能看懂。</p><h3 id="数组越界" tabindex="-1"><a class="header-anchor" href="#数组越界" aria-hidden="true">#</a> 数组越界</h3><p>在我们进行数组操作的时候，最容易遇到的一个问题就是数组越界，也就是 ArrayIndexOutOfBoundsException <a href="https://javabetter.cn/exception/gailan.html" target="_blank" rel="noopener noreferrer">异常<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>anArray<span class="token punctuation">[</span><span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>上面这段代码就会抛出数组越界的异常，因为数组的索引是从 0 开始的，所以最大索引为 <code>length - 1</code>，也就是 4，所以当我们使用 5 作为索引的时候，就会抛出异常。</p><p>所以在操作数组之前，一定要注意索引的范围。</p><h3 id="小结" tabindex="-1"><a class="header-anchor" href="#小结" aria-hidden="true">#</a> 小结</h3><p>好，今天我们就先讲到这里，说完，我就跑去阳台来一根华子，留三妹在电脑前面练习了起来。</p><hr><p>GitHub 上标星 10000+ 的开源知识库《<a href="https://github.com/itwanger/toBeBetterJavaer" target="_blank" rel="noopener noreferrer">二哥的 Java 进阶之路<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>》第一版 PDF 终于来了！包括Java基础语法、数组&字符串、OOP、集合框架、Java IO、异常处理、Java 新特性、网络编程、NIO、并发编程、JVM等等，共计 32 万余字，500+张手绘图，可以说是通俗易懂、风趣幽默……详情戳：<a href="https://javabetter.cn/overview/" target="_blank" rel="noopener noreferrer">太赞了，GitHub 上标星 10000+ 的 Java 教程<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a></p><p>微信搜 <strong>沉默王二</strong> 或扫描下方二维码关注二哥的原创公众号沉默王二，回复 <strong>222</strong> 即可免费领取。</p><figure><img src="https://cdn.tobebetterjavaer.com/tobebetterjavaer/images/gongzhonghao.png" alt="" tabindex="0" loading="lazy"><figcaption></figcaption></figure></div><!----><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/itwanger/toBeBetterJavaer/edit/master/docs/array/array.md" rel="noopener noreferrer" target="_blank" aria-label="编辑此页" class="nav-link label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="meta-item git-info"><div class="update-time"><span class="label">上次编辑于: </span><!----></div><div class="contributors"><span class="label">贡献者: </span><!--[--><!--[--><span class="contributor" title="email: www.qing_gee@163.com">itwanger</span>,<!--]--><!--[--><span class="contributor" title="email: www.qing_gee@163.com">沉默王二</span><!--]--><!--]--></div></div></footer><nav class="vp-page-nav"><!----><a class="vp-link nav-link next" href="/array/double-array.html"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">二维数组<!----></div></a></nav><div id="comment" class="giscus-wrapper input-top" style="display:none;"><div class="loading-icon-wrapper" style="display:flex;align-items:center;justify-content:center;height:96px"><svg xmlns="http://www.w3.org/2000/svg" width="48" height="48" preserveAspectRatio="xMidYMid" viewBox="25 25 50 50"><animateTransform attributeName="transform" type="rotate" dur="2s" keyTimes="0;1" repeatCount="indefinite" values="0;360"></animateTransform><circle cx="50" cy="50" r="20" fill="none" stroke="currentColor" stroke-width="4" stroke-linecap="round"><animate attributeName="stroke-dasharray" dur="1.5s" keyTimes="0;0.5;1" repeatCount="indefinite" values="1,200;90,200;1,200"></animate><animate attributeName="stroke-dashoffset" dur="1.5s" keyTimes="0;0.5;1" repeatCount="indefinite" values="0;-35px;-125px"></animate></circle></svg></div></div><!----><!--]--></main><!--]--><footer class="vp-footer-wrapper"><div class="vp-footer"><a href="https://beian.miit.gov.cn/" target="_blank">豫ICP备2021038026号-4</a><img src="https://cdn.tobebetterjavaer.com/tobebetterjavaer/images/beian.png" height="15px" width="15px" /><a target="_blank" href="http://www.beian.gov.cn/portal/registerSystemInfo?recordcode=41030502000411"><span>豫公网安备 41030502000411号</span></a></div><div class="vp-copyright">Copyright © 2024 沉默王二</div></footer></div><!--]--><!----><!----><!--]--></div>
<script type="module" src="/assets/app-b1913f48.js" defer></script>
</body>
</html>