import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

public class Test {

    public static void main(String[] args) {      
       String[] array=new String[]{
               "1","2","3","4"
       };
       listAll(Arrays.asList(array),"");
    }
    public static void listAll(List candidate,String prefix){
        System.out.println(prefix);
        for(int i=0;i<candidate.size();i++){
            List temp = new LinkedList(candidate);
            listAll(temp,prefix+temp.remove(i));
        }
    }
}

for(int i=0;i<candidate.size();i++){
            List temp = new LinkedList(candidate);
            listAll(temp,prefix+temp.remove(i));
        }