package class026;

import java.util.HashMap;

import java.util.HashSet;

public class Code01_HashSetAndHashMap {

public static void main(String[] args) {

// Integer、Long、Double、Float

// Byte、Short、Character、Boolean

// String等都有这个特征

String str1 = new String("Hello");

String str2 = new String("Hello");

// false，因为不同的内存地址

System.out.println(str1 == str2);

// true，因为它们的值是相同的

System.out.println(str1.equals(str2));

HashSet<String> set = new HashSet<>();

set.add(str1);

System.out.println(set.contains("Hello"));

System.out.println(set.contains(str2));

set.add(str2);

System.out.println(set.size());

set.remove(str1);

set.clear();

System.out.println(set.isEmpty());

System.out.println("===========");

HashMap<String, String> map1 = new HashMap<>();

map1.put(str1, "World");

System.out.println(map1.containsKey("Hello"));

System.out.println(map1.containsKey(str2));

System.out.println(map1.get(str2));

System.out.println(map1.get("你好") == null);

map1.remove("Hello");

System.out.println(map1.size());

map1.clear();

System.out.println(map1.isEmpty());

System.out.println("===========");

// 一般在笔试中，未必需要申请哈希表

HashMap<Integer, Integer> map2 = new HashMap<>();

map2.put(56, 7285);

map2.put(34, 3671263);

map2.put(17, 716311);

map2.put(24, 1263161);

// 上面的map2行为，可以被如下数组的行为替代

int[] arr = new int[100];

arr[56] = 7285;

arr[34] = 3671263;

arr[17] = 716311;

arr[24] = 1263161;

// 哈希表的增、删、改、查，都可以被数组替代，前提是key的范围是固定的、可控的

System.out.println("在笔试场合中哈希表往往会被数组替代");

System.out.println("===========");

Student s1 = new Student(17, "张三");

Student s2 = new Student(17, "张三");

HashMap<Student, String> map3 = new HashMap<>();

map3.put(s1, "这是张三");

System.out.println(map3.containsKey(s1));

System.out.println(map3.containsKey(s2));

map3.put(s2, "这是另一个张三");

System.out.println(map3.size());

System.out.println(map3.get(s1));

System.out.println(map3.get(s2));

}

public static class Student {

public int age;

public String name;

public Student(int a, String b) {

age = a;

name = b;

}

}

}