java8新特性_08_筛选与切片_filter": { "terms": { "salary": [6666,7777] }java-优快云博客

本文链接：https://blog.youkuaiyun.com/to_real/article/details/108338791

本文详细介绍Java Stream API中的筛选与切片操作，包括filter过滤、limit限制、skip跳过及distinct去重功能。通过实例演示如何使用这些操作处理集合数据，如过滤年龄大于35岁的员工、限制显示高薪员工的数量、跳过前几个元素以及去除重复的员工记录。

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筛选与切片：
filter —— 接收 Lambda，从流中排除某些元素；
limit —— 截断流，使其元素不超过给定数量；
skip(n) —— 跳过元素，返回一个仍掉了前 n 个元素的流。若流中元素不足 n 个，则返回一个空流。与 limit(n) 互补；
distinct —— 筛选，通过流所生成元素的 hashCode() 和 equals() 去除重复元素。

    List<Employe> employes = Arrays.asList(
            new Employe("张三", 18,9999.99),
            new Employe("李四", 38,5555.99),
            new Employe("王五", 50,6666.66),
            new Employe("赵六", 16,3333.33),
            new Employe("田七", 10,7777.77),
            new Employe("田七", 10,7777.77),
            new Employe("田七", 10,7777.77)
    );

    //filter 过滤
    @Test
    public void test1(){
        employes.stream()//创建流
                .filter(e->e.getAge() >= 35)//中间操作
                .forEach(System.out::println);//终止操作
    }

    //limit 限制
    @Test
    public void test2(){
        employes.stream()
                .filter(e->e.getSalary() >= 5000)
                .limit(2)
                .forEach(System.out::println);
    }

    //skip(n) 跳过
    @Test
    public void test3(){
        employes.stream()
                .filter(e -> e.getSalary() >= 5000)
                .skip(2)
                .forEach(System.out::println);
    }

    //distinct 去重,通过hashCode() 和 equals() 去重
    @Test
    public void test4(){
        employes.stream()
                .distinct()
                .forEach(System.out::println);
    }
}

注意：distinct 去重的时候，Employee.java 中要覆写 equals() 和 hashCode() 方法：

package com.lambda1;

import java.util.Objects;

public class Employe {

    private String name;
    private int age;
    private double salary;

    public Employe() {
    }

    public Employe(String name, int age, double salary) {
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Employe employe = (Employe) o;
        return age == employe.age &&
                Double.compare(employe.salary, salary) == 0 &&
                Objects.equals(name, employe.name);
    }

    @Override
    public int hashCode() {

        return Objects.hash(name, age, salary);
    }

    @Override
    public String toString() {
        return "Employe{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", salary=" + salary +
                '}';
    }
}