遇到这个java.lang.Integer cannot be cast to study.exa1

[NULLRain]

package study;

import java.util.Comparator;
import java.util.Set;
import java.util.TreeMap;

public class exa1
{
int no;
public exa1(int aa){
no=aa;
}

public static void main(String[] args)
{
@SuppressWarnings("unchecked")
TreeMap a =new TreeMap(new Comparator()
{
public int compare(Object arg0, Object arg1)
{
exa1 a=(exa1)arg1;
exa1 b=(exa1)arg0;
return a.no-b.no;
}
}
);
a.put(new exa1(122),"a");
a.put(new exa1(2),"b");
a.put(new exa1(223),"b");
System.out.println(a.get(1));
System.out.println(a.entrySet());
}
}

运行之后报java.lang.Integer cannot be cast to study.exa1
不知道怎么改呀，希望各位朋友帮帮我

[NULLRain]

谢谢你啊，我一直以为问题出在中间那块，怪不得一直找不到

[鱿鱼ing]

ClassCastException--如果指定键不能与映射中的当前键进行比较，抛出此异常。 a.get(1) a是treemap 里面没有1这个key 修改为一下可以输出 System.out.println(a.get(new exa1(122))); System.out.println(a.get(new exa1(2))); System.out.println(a.get(new exa1(223))); 具体看http://www.yiibai.com/java/util/treemap_get.html