【java学习】第十四天(集合3-Set接口)

Set接口

Set接口基本介绍

Set接口的常用方法

Set接口的遍历方式

HashSet类的全面说明

HashSet 底层机制说明

课后练习题

实现代码

package com.quange.test;


import java.util.HashSet;
import java.util.Objects;


public class test06 {
    public static void main(String[] args) {

        HashSet hashSet = new HashSet();
        hashSet.add(new Employee("tom", 2000, new MyDate(2022,1,2)));
        hashSet.add(new Employee("sal", 3000, new MyDate(2022,1,3)));
        hashSet.add(new Employee("tom", 2000, new MyDate(2022,1,2)));

        System.out.println(hashSet);

    }
}

class Employee{
    private String name;
    private int sal ;
    private MyDate birthday;

    public Employee(String name, int sal, MyDate birthday) {
        this.name = name;
        this.sal = sal;
        this.birthday = birthday;
    }


    public String getName() {
        return name;
    }

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

    public int getSal() {
        return sal;
    }

    public void setSal(int sal) {
        this.sal = sal;
    }

    public MyDate getBirthday() {
        return birthday;
    }

    public void setBirthday(MyDate birthday) {
        this.birthday = birthday;
    }

    // 重写equals 方法,判断name 和 birthday
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Employee employee = (Employee) o;
        return Objects.equals(name, employee.name) && Objects.equals(birthday, employee.birthday);
    }

    // 重写hashCode  方法，判断name 和birthday
    @Override
    public int hashCode() {
        return Objects.hash(name, birthday);
    }

    // 重写toString方法
    @Override
    public String toString() {
        return "Employee{" +
                "name='" + name + '\'' +
                ", sal=" + sal +
                ", birthday=" + birthday +
                '}';
    }
}



class MyDate{
    private int year;
    private int month;
    private int day;

    public MyDate(int year, int month, int day) {
        this.year = year;
        this.month = month;
        this.day = day;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public int getMonth() {
        return month;
    }

    public void setMonth(int month) {
        this.month = month;
    }

    public int getDay() {
        return day;
    }

    public void setDay(int day) {
        this.day = day;
    }

    // 重写 equals 方法，判断年月日
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        MyDate myDate = (MyDate) o;
        return year == myDate.year && month == myDate.month && day == myDate.day;
    }

    // 重写 hashCode 方法，判断年月日
    @Override
    public int hashCode() {
        return Objects.hash(year, month, day);
    }

    // 重写 toString 方法
    @Override
    public String toString() {
        return "MyDate{" +
                "year=" + year +
                ", month=" + month +
                ", day=" + day +
                '}';
    }
}

输出，第三个对象未能添加

[Employee{name='tom', sal=2000, birthday=MyDate{year=2022, month=1, day=2}}, Employee{name='sal', sal=3000, birthday=MyDate{year=2022, month=1, day=3}}]