stream流的使用_stream流使用-优快云博客

本文链接：https://blog.youkuaiyun.com/ccxlct/article/details/126390728

这篇博客演示了如何使用Java Stream API进行数据操作，包括排序、过滤、查找最大值、检查条件以及组合条件等操作。示例中展示了对包含人物信息的列表进行不同条件的处理，如按年龄排序、筛选名字长度和年龄条件等。

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package co.springcloud.controller;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import lombok.Data;
import lombok.experimental.Accessors;
/**
 * @author XX
 * @version $Id: StreamController.java, v 0.1 2022-08-17 10:34 XX.pt Exp $$
 */
public class StreamController {
    public static void main(String[] args) {
        List<People> list = new ArrayList<>();
        list.add(new People(1,"任嘉伦",32));
        list.add(new People(2,"池昌旭",33));
        list.add(new People(3,"白敬亭",29));
        list.add(new People(4,"黄明昊",21));
        list.add(new People(5,"张艺兴",30));
        list.add(new People(6,"王鹤棣",28));
        list.add(new People(7,"杨洋",30));
        list.add(new People(8,"迪丽热巴",28));
        System.out.println("------------------------");
        System.out.println("按照年龄从大到小排序");                list.stream().sorted(Comparator.comparing(People::getAge).reversed()).forEach(System.out::println);
        System.out.println("按照年龄从小到大排序");
        list.stream().sorted(Comparator.comparing(People::getAge)).forEach(System.out::println);
        System.out.println("只返回名字长度大于2的");
        list.stream().filter(people -> people.getName().length()>2).forEach(System.out::println);
        System.out.println("返回id最大的那个");
        System.out.println(list.stream().max(Comparator.comparing(people -> people.getId())));
        System.out.println("list中的年龄都大于30岁吗(所有满足条件返回true，否则false)");
        System.out.println(list.stream().allMatch(people -> people.getAge()>30));
        System.out.println("list中的年龄都大于18岁吗");
        System.out.println(list.stream().allMatch(people -> people.getAge()>18));
        System.out.println("年龄有大于30的吗(有一个满足条件的就返回true)");
        System.out.println(list.stream().anyMatch(people -> people.getAge()>30));
        System.out.println("找出名字长度大于2的且年龄大于30的人(注意：过滤两次之后或者是多个条件之后要转成list）--------");
        System.out.println(list.stream().filter(people -> people.getName().length()>2).filter(people -> people.getAge()>30).collect(Collectors.toList()));
        System.out.println(list.stream().filter(people -> people.getName().length()>2 && people.getAge()>30).collect(Collectors.toList()));
        System.out.println("找出名字长度大于等于3的且年龄最大的");
        System.out.println(list.stream().filter(people -> people.getName().length()>=3).max(Comparator.comparing(people -> people.getAge())));
        System.out.println("取年龄大于30且名字长度最长的");
        System.out.println(list.stream().filter(people -> people.getAge()>30).max(Comparator.comparing(people -> people.getName().length())));
        System.out.println("大于30岁的有几人");
        System.out.println(list.stream().filter(people -> people.getAge()>30).count());
        System.out.println("岁数一样大的放一起");
        System.out.println(list.stream().collect(Collectors.groupingBy(people -> people.getAge())));
    }

    @Data
    @Accessors(chain = true)
    public static class People{
        private int id;
        private String name;
        private int age;
        public People(int id, String name, int age) {
            this.id = id;
            this.name = name;
            this.age = age;
        }
        public People() {
        }
    }
}