学步园

一、整体代码

       HashSet.java

import java.util.*;

class HashSetTest 
{

    public static void sop(Object obj)
    {
        System.out.println(obj);
    }
    public static void main(String[] args) 
    {
        HashSet<Person> hs = new HashSet<Person>();
        hs.add(new Person("a1",11));
        hs.add(new Person("a2",12));
        hs.add(new Person("a3",13));
        hs.add(new Person("a2",12));
        hs.add(new Person("a4",14));
        //sop("a1:"+hs.contains(new Person("a2",12)));
        //hs.remove(new Person("a4",13));
        Iterator<Person> it = hs.iterator();
        while(it.hasNext())
        {
            Person p = it.next();
            sop(p.getName()+"::"+p.getAge());    
        }

    }

}

class Person
{
    private String name;
    private int age;

    Person(String name,int age)
    {
        this.name = name;
        this.age = age;
    }
    public int hashCode()
    {
        //System.out.println(this.name+"....hashCode");
        return name.hashCode()+age*37;
    }
    public boolean equals(Object obj)
    {
        if(!(obj instanceof Person))
        return false;
        Person p = (Person)obj;
        //System.out.println(this.name+"...equals.."+p.name);
        return this.name.equals(p.name) && this.age == p.age;
    }
    public String getName()
    {
        return name;
    }

    public int getAge()
    {
        return age;
    }
}

二、解释

        HashSet装的元素无序，也不可重复。判断是否重复的依据是hashCode和equals，先看hashCode

       代码地址：https://github.com/jltxgcy/Demo