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+")";}@Overrideprotected 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;}}