Java Lambda常用方法（持续更新）

package com.svnlan.order.controller;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class TestClass {
    public static void main(String[] args) {
        User user1 = new User(5, "aa");
        User user2 = new User(2, "ba");
        User user3 = new User(3, "ac");
        User user4 = new User(1, "aad");
        User user5 = new User(4, "asd");
        List<User> userList = Arrays.asList(user1, user2, user3, user4, user5);
        //获取所有ID集合
        List<Integer> idList = userList.stream().map(User::getId).collect(Collectors.toList());
        //排序ID
        List<User> userList1 = userList.stream().sorted(Comparator.comparingInt(User::getId)).collect(Collectors.toList());
        //分组
        Map<String, Long> map = userList.stream().collect(Collectors.groupingBy(User::getName, Collectors.counting()));
        //获取id大于2的
        List<User> userList2 = userList.stream().filter(user -> user.getId() > 2).collect(Collectors.toList());
        //获取最大
        Integer id = userList.stream().map(User::getId).max(Integer::compareTo).get();
        //获取最小
        Integer id1 = userList.stream().map(User::getId).min(Integer::compareTo).get();
        //获取id数量
        long count = userList.stream().map(User::getId).count();
        //总和
        int sum = userList.stream().mapToInt(User::getId).sum();
        //获取平均值
        double d = userList.stream().mapToInt(User::getId).average().getAsDouble();
        //匹配findAny/allMatch/noneMatch多用来判断
        User user = userList.stream().findAny().get();
        //获取第一个对象
        User user6 = userList.stream().findFirst().get();
        //将名字全转换为大写
        List<String> list = userList.stream().map(User::getName).map(String::toUpperCase).collect(Collectors.toList());
        //获取忽略第一个并取前几条数据
        List<User> list1 = userList.stream().skip(1).limit(2).collect(Collectors.toList());
        //去重
        List<User> collect = userList.stream().distinct().collect(Collectors.toList());

    }
}