package lambda;

import java.util.Arrays;

import java.util.List;

import java.util.concurrent.TimeUnit;

import java.util.function.BiFunction;

import java.util.stream.Stream;

public final class Lambda {

private Lambda() {

}

static class Person implements Named, EchoName {

private String name;

Person(String name) {

this.name = name;

}

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public String toString() {

return String.format("My name is %s", this.name);

}

@Override

public String echoName() {

return Named.super.echoName(); // 重名了必须要手动指定实现

}

}

static interface Named {

default String echoName() { // 默认方法的实现

return "SamChi";

}

}

static interface EchoName {

default String echoName() {

return "James";

}

}

public static void main(String[] args) {

List<String> strList =

Arrays.asList("Sam", "Jack", "Peter", "Tom", "Lucy", "Anders", "James", "Lily");

System.out.println("before sort:" + strList);

strList.sort((str1, str2) -> Integer.compare(str1.length(), str2.length())); // 根据泛型来自动推导

System.out.println("after sort:" + strList);

strList.forEach(str -> System.out.println(String.format("= %s =", str))); // 可类型推导的单个参数无需加小括号

strList.forEach((final String str) -> System.out.println(String.format("= %s =", str))); // 可以加final修饰符

// java.util.function包中的函数式接口

BiFunction<String, String, Integer> comparator =

(str1, str2) -> Integer.compare(str1.length(), str2.length());

System.out.println(comparator instanceof Object);

System.out.println(comparator.getClass().getCanonicalName());

Object obj = comparator;

System.out.println(obj.getClass().getCanonicalName());

// obj = (String str1, String str2) -> Integer.compare(str1.length(), str2.length()); 这样引用就不可以了。

Runnable sleeper = () -> {

System.out.println("Zzzzzz");

try {

TimeUnit.SECONDS.sleep(1L);

} catch (InterruptedException e) {

e.printStackTrace(); // 在Lambda表达式中捕获异常

}

};

Thread t = new Thread(sleeper);

t.start();

strList.forEach(str -> System.out.println(str));

strList.forEach(System.out::println);

strList.sort(String::compareToIgnoreCase);

Stream<Person> personsStream = strList.stream().map(Person::new);

personsStream.forEach(System.out::println);

int a = 0, b = 1;

new Thread(() -> {

System.out.println("a is :" + a);

System.out.println("b is :" + b);

// a++; 不可以改变外围作用域的值

// int a = 3; 不可以覆盖定义外围作用域的值

}).start();

Person p = new Person("Jack");

System.out.println(">>>>>" + p.getName());

}

}