在下列E类中System.out.println的输出结果是

import java.util.*;
public class E{
    public static void main(String args[]){
        Stack<Character> mystack1=new Stack<Character>(),
                mystack2=new Stack<Character>();
        StringBuffer bu =new StringBuffer();
        for(char c='A';c<='D';c++){
                mystack1.push(new Character(c));
        }
        while(!(mystack1.empty())){
                Character temp=mystack1.pop();
                mystack2.push(temp);
        }
        while(!(mystack2.empty())){
                Character temp=mystack2.pop();
                bu.append(temp.charValue());
        }
        System.out.println(bu);
    }
}