把一个数组中的组合全部列出 [1,2] 1, 12, 2,21

package day20170107;


import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class Combination {

public static void listAll(List candidate,String preifx){
//if(candidate.isEmpty()){
System.out.println(preifx);
//}
for(int i=0;i<candidate.size();i++){
List temp=new ArrayList(candidate);
listAll(temp,preifx+temp.remove(i));
}
}
public static void main(String[] args) {
String []arr={"1","2"};
listAll(Arrays.asList(arr),"");
}

}