JAVA8 Lambda表达式基础使用

/*** JAVA8 Lambda表达式基础使用* GitHub地址：https://github.com/hack-feng/algorithm* CSDN地址：https://blog.csdn.net/qq_34988304/article/details/100920460* 联系作者：1150640979@qq.com*/
public class Lambda {@SuppressWarnings("OptionalGetWithoutIsPresent")public static void main(String[] args) throws InterruptedException {System.out.println("-----------------------1、Lambda的多线程写法--------------------------");// 普通new Thread(new Runnable() {@Overridepublic void run() {System.out.println("非Lambda的多线程写法");}}).start();// Lambdanew Thread(() -> System.out.println("Lambda的多线程写法")).start();Thread.sleep(100);System.out.println("-----------------------2、Lambda的for循环写法--------------------------");List<String> forTestList = new ArrayList<>();forTestList.add("a");forTestList.add("b");forTestList.add("c");for (int i = 0; i < forTestList.size(); i++) {System.out.println("普通for循环" + forTestList.get(i));}for (String flag : forTestList) {System.out.println("forEach循环" + flag);}forTestList.forEach(list -> System.out.println("Lambda的写法" + list));System.out.println("-----------------------3、Lambda集合常用的操作--------------------------");System.out.println("初始化数据：");List<User> userList = new ArrayList<>();for (int i = 0; i < 10; i++) {User user = new User(i, "姓名"+ i,  new Random().nextInt(5));System.out.println(user.toString());userList.add(user);}System.out.println("根据age分组--------------------------------------------------------");Map<Integer ,List<User>> groupMap = userList.stream().collect(Collectors.groupingBy(User::getAge));for(Map.Entry map : groupMap.entrySet()){System.out.println(map.getKey() + "    " + map.getValue());}System.out.println("根据age过滤--------------------------------------------------------");List<User> filerList = userList.stream().filter(list -> list.getAge() == 3).collect(Collectors.toList());filerList.forEach(list -> System.out.println("age为3的数据有：" + list.toString()));System.out.println("根据age, id进行倒序排序----------------------------------------------------");userList.sort(Comparator.comparing(User::getAge).thenComparing(User::getId).reversed());userList.forEach(list -> System.out.println(list.toString()));System.out.println("list转为map---------------------------------------------------------------");Map<Integer, User> map = userList.stream().collect(Collectors.toMap(User :: getId, list -> list));map.forEach((k, v) -> System.out.println("id:" + k + "            value:" + v.toString()));System.out.println("打印map中value的值age为3的id-----------------------------------------------");map.forEach((k, v) -> {if(v.getAge() == 3){System.out.println("age的值为3的id是：" + k);}});System.out.println("取数据的最大值和最小值-------------------------------------------------------");Integer maxId = userList.stream().map(User::getId).max(Integer::compareTo).get();System.out.println("最大id值为：" + maxId);Integer minId = userList.stream().map(User::getId).min(Integer::compareTo).get();System.out.println("最小id值为：" + minId);}// 定义User类，用作测试使用static class User{private Integer id;private String name;private Integer age;User(Integer id, String name, Integer age){this.id = id;this.name = name;this.age = age;}Integer getId() {return id;}Integer getAge() {return age;}public String toString(){return "id="+this.id + ",name="+this.name+",age="+this.age;}}
}