Java字符串进行组合

输入ABC，输出：

A

AB
ABC
AC
B
BC

C

package test;
import java.util.*;
public class testOne {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            String s1 = in.nextLine();
            String[] s2 = new String[s1.length()];
            for(int i = 0;i < s1.length();i++){
                s2[i] = s1.charAt(i)+"";
            }
            listAll(Arrays.asList(s2),"");
        }
    }
    public static void listAll(List candidate,String prefix){
        if(!"".equals(prefix)){
            System.out.println(prefix);
        }
        for(int i=0;i

输出：