帮帮忙。很简单的 User user1//User类没有放在同一目录,并且没有 import进来. 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 放在一起了package untitled6;import java.util.*;public class ArrayListDeml { public static void main(String[] args){ User user1=new User("chen","6898397"); User user2=new User("jean","6296336"); User user3=new User("tao","1111111"); ArrayList userlist=new ArrayList(); userlist.add(user1); userlist.add(user2); userlist.add(user3); Collections.sort(userlist); Iterator iterator=userlist.iterator(); while(iterator.hasNext()){ User user=(User)iterator.next(); System.out.println(user.getUsername()); } }}package untitled6;import java.util.*;public class User { String username; String phonenumber; public User() { } public User(String username,String phonenumber){ this.username=username; this.phonenumber=phonenumber; } public void setUsername(String username){ this.username=username; } public String getUsername(){ return username; } public void setPhonenumber(String phonenumber){ this.phonenumber=phonenumber; } public String getPhonenumber(){ return phonenumber; }} 将cast的那行代码改为User user=(User)(iterator.next());试试 问题出在这句话:Collections.sort(userlist);对象排序,应该implements接口Comparable 你的user类没有实现Comparable接口!!!!!!!!! Netbeans GUI 运行效果 问题 int compareTo(Object o)中的o到底是什么啊? 找不到symantec的类库,请帮助! java怎么调用flash(swf)或者gif呢 怎么掉出帮助文档 struts 添加数据问题,! 数据库问题 SUN StarSuite6.0下载 一个rmi的小问题,在线等待,结决马上结帐? 请问:哪有mobile agent的源代码例子?推荐一下 怎样在一张已经显示的大图上再贴一张小图,而且小图可以用鼠标来拖拉确定位置 帮忙看一看jtable的代码,为什么多了一列?
package untitled6;
import java.util.*;
public class ArrayListDeml {
public static void main(String[] args){
User user1=new User("chen","6898397");
User user2=new User("jean","6296336");
User user3=new User("tao","1111111");
ArrayList userlist=new ArrayList();
userlist.add(user1);
userlist.add(user2);
userlist.add(user3);
Collections.sort(userlist);
Iterator iterator=userlist.iterator();
while(iterator.hasNext()){
User user=(User)iterator.next();
System.out.println(user.getUsername());
}
}
}package untitled6;
import java.util.*;
public class User {
String username;
String phonenumber;
public User() {
}
public User(String username,String phonenumber){
this.username=username;
this.phonenumber=phonenumber;
}
public void setUsername(String username){
this.username=username;
}
public String getUsername(){
return username;
}
public void setPhonenumber(String phonenumber){
this.phonenumber=phonenumber;
}
public String getPhonenumber(){
return phonenumber;
}
}
User user=(User)(iterator.next());试试
Collections.sort(userlist);
对象排序,应该implements接口Comparable