内部类、HashSet

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原创最新推荐文章于 2026-05-19 09:19:18 发布 116 阅读 AI 写同款· GEO 优化 ›

机器学习发展历史及现状（重要的期刊，会议，大牛总结） 1 引言机器学习是指通过计算机学习数据中的内在规律性信息，获得新的经验和知识，以提高计算机的智能性，使计算机能够像人那样去决策。随着各行业对数据的需求量增多，对处理和分析数据的效率要求变高，一系列机器学习算法应运而生。机器学习算法主要是指通过数学及统计方法求解最优化问题的步骤和过程。针对不同的数据和不同模型需求，选择和使用适当的的机器学习算法可以更高效地解决一些实际问题。本文将从机器学习的起源... 阅读详情

package enumeration;

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

public class HashSet_ {
    public static void main(String[] args) {
        HashSet hashSet = new HashSet();

        Employee milan = new Employee("milan", 12500, new Employee.MyDate(2021, 11, 20));
        Employee jack = new Employee("jack", 12500, new Employee.MyDate(2021, 11, 20));
        Employee tom = new Employee("milan", 12500, new Employee.MyDate(2021, 11, 20));
        hashSet.add(milan);
        hashSet.add(jack);
        hashSet.add(tom);
        System.out.println("hashSet.size = " +hashSet.size());
        System.out.println("hashSet = " + hashSet );
        //重写他们的hashCode,如果name 和Age一样就放回相同的hashCode
//        System.out.println(hashSet);
    }
}

class Employee{
    private String name;
    private double sal;
    private MyDate myDate;

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

    public Employee(String name, double sal, MyDate myDate) {
        this.name = name;
        this.sal = sal;
        this.myDate = myDate;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Employee employee = (Employee) o;
        return Double.compare(employee.sal, sal) == 0 &&
                Objects.equals(name, employee.name) &&
                Objects.equals(myDate, employee.myDate);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, sal, myDate);
    }

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

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

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

        @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;
        }

        @Override
        public int hashCode() {
            return Objects.hash(year, month, day);
        }
    }
    }

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