java排列组合出所有的结果

 import java.util.*;
public class FullPermutation 
{
    public static void main(String[] args) 
    {
        System.out.println("Hello World!");
        List<String[]> list = new ArrayList<String[]>();
        String[] str = new String[1];
        str[0] = "a1";
        list.add(str);
        str = new String[3];
        str[0] = "b1";
        str[1] = "b2";
        str[2] = "b3";
        list.add(str);
        str = new String[2];
        str[0] = "c1";
        str[1] = "c2";
        list.add(str);
        str = new String[2];
        str[0] = "e1";
        str[1] = "e2";
        list.add(str);
        str = new String[4];
        str[0] = "d1";
        str[1] = "d2";
        str[2] = "d3";
        str[3] = "d4";
        list.add(str);
        for(String[] s : list){
            System.out.println(Arrays.toString(s));
        }
        System.out.println("--------------");
        fullPermutation(list,0,null);
    }
    public static void fullPermutation(List<String[]> list,int index,List<String> result){
        if(index == list.size()){
            System.out.println(result);
            return;
        }
        String[] s = list.get(index);
        for(int i = 0; i < s.length; i++){
          if(index == 0){
                result = new ArrayList<String>();
                result.add(s[i]);
            }
          else{
                result.add(s[i]);
            }
            fullPermutation(list,index + 1,result);
            result.remove(s[i]);
        }
    }
}