testhashset.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
 */

//类A的equals方法总是返回true,但没有重写其hashCode()方法
class A
{
	public boolean equals(Object obj)
	{
		return true;
	}
}
//类B的hashCode()方法总是返回1,但没有重写其equals()方法
class B
{
	public int hashCode()
	{
		return 1;
	}
}
//类C的hashCode()方法总是返回2,但没有重写其equals()方法
class C
{
	public int hashCode()
	{
		return 2;
	}
	public boolean equals(Object obj)
	{
		return true;
	}
}
public class TestHashSet
{
	public static void main(String[] args) 
	{
		HashSet books = new HashSet();
		//分别向books集合中添加2个A对象，2个B对象，2个C对象
		books.add(new A());
		books.add(new A());
		books.add(new B());
		books.add(new B());
		books.add(new C());
		books.add(new C());
		System.out.println(books);
	}
}