testhashset2.java

疯狂Java讲义_源码(含Java设计模式CHM

import java.util.*;
/**
 * Description:
 * <br/>Copyright (C), 2005-2008, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee [e-mail]
 * @version  1.0
 */
class R
{
	int count;
	public R(int count)
	{
		this.count = count;
	}
	public String toString()
	{
		return "R(count属性:" + count + ")";
	}
	public boolean equals(Object obj)
	{
		if (obj instanceof R)
		{
			R r = (R)obj;
			if (r.count == this.count)
			{
				return true;
			}
		}
		return false;
	}
	public int hashCode()
	{
		return this.count;
	}
}
public class TestHashSet2
{
	public static void main(String[] args) 
	{
		HashSet hs = new HashSet();
		hs.add(new R(5));
		hs.add(new R(-3));
		hs.add(new R(9));
		hs.add(new R(-2));
		//打印TreeSet集合，集合元素是有序排列的
		System.out.println(hs);
		//取出第一个元素
		Iterator it = hs.iterator();
		R first = (R)it.next();
		//为第一个元素的count属性赋值
		first.count = -3;
		//再次输出count将看到TreeSet里的元素处于无序状态
		System.out.println(hs);
		hs.remove(new R(-3));
		System.out.println(hs);
		//输出false
		System.out.println("hs是否包含count为-3的R对象？" + hs.contains(new R(-3)));
		//输出false
		System.out.println("hs是否包含count为5的R对象？" + hs.contains(new R(5)));

	}
}