遍历集合增删改所引发的问题

package com.test;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.CopyOnWriteArrayList;

public class ThreadTest10
{

	/**
	 * @param args
	 */
	public static void main(String[] args)
	{
		Collection users = /*new CopyOnWriteArrayList();*/new ArrayList();
		users.add(new User("张三",28));
		users.add(new User("李四",25));
		users.add(new User("王五",31));
		Iterator it = users.iterator();
		
		while(it.hasNext()){
			User user = (User)it.next();
			if("张三".equals(user.getName())){
				users.remove(user);
			}else{
				System.out.println(user);
			}
		}
	}

}

class User implements Cloneable
{
	private String name;
	private int age;

	public User(String name, int age)
	{
		this.name = name;
		this.age = age;
	}

	public boolean equals(Object obj)
	{
		if (this == obj)
		{
			return true;
		}
		if (!(obj instanceof User))
		{
			return false;
		}
		User user = (User) obj;
		if (this.name.equals(user.name) && this.age == user.age)
		{
			return true;
		}
		return false;
	}
	
	public int hashCode(){
		return name.hashCode()+age;
	}
	
	public String toString(){
		return "(name:'"+name+"',age:"+age+")";
	}
	
	@Override
	protected Object clone()
	{
		Object object = null;
		try{
			object = super.clone();
		}catch(CloneNotSupportedException e){
			
		}
		return object;
	}

	public String getName()
	{
		return name;
	}

	public void setName(String name)
	{
		this.name = name;
	}

	public int getAge()
	{
		return age;
	}

	public void setAge(int age)
	{
		this.age = age;
	}
}