一般描述的事物需要往集合中新增，那麼都需要重寫這兩個方法

刪除和判斷元素是否存在，都是先判斷hashCode 看看是否存在，若存在則繼續equals（）；

import java.util.*;
class Person
{
	private String name;
	private int age;
	Person(String name,int age)
	{
		this.name=name;
		this.age=age;
	}
	public int hashCode()//重寫  
	{
		return name.hashCode()+age ;
	}
	public boolean equals(Object obj)//重寫   Object不能換
	{
          if(!(obj instanceof Person))
			  return false;
		  Person p=(Person)obj;

		  System.out.println(this.name+"...."+p.name);

		  return this.name.equals(p.name)&&this.age==p.age;
	}
	public String getName()
	{
		return name;
	}
	public int getAge()
	{
		return age;
	}
}
class HashSetDemo 
{
	public static void main(String[] args) 
	{
		HashSet hs=new HashSet();

		hs.add(new Person("lisi01",30));
		hs.add(new Person("lisi02",33));
		hs.add(new Person("lisi03",35));
		hs.add(new Person("lisi02",33));
		hs.add(new Person("lisi01",30));
		hs.add(new Person("lisi04",32));
		hs.add(new Person("lisi03",35));

		Iterator it=hs.iterator();

		while(it.hasNext())
		{
           Person p=(Person)it.next();;
		   sop(p.getName()+" "+p.getAge());
		}
	}
	public static void sop(Object obj)
    {
          System.out.println(obj);

	}
}