按字母顺序排序ArrayList

Question

我试图找到字符串的所有排列并按字母顺序排序.

这是我到目前为止:

public class permutations {

        public static void main(String args[]) {
            Scanner s = new Scanner(System.in);
            System.out.print("Enter String: ");
            String chars = s.next();
            findPerms("", chars);
        }

        public static void findPerms(String mystr, String chars) {

            List<String> permsList = new ArrayList<String>();

                if (chars.length() <= 1)
                        permsList.add(mystr + chars);
                        //System.out.print(mystr + chars + " ");

                else
                        for (int i = 0; i < chars.length(); i++) {
                            String newString = chars.substring(0, i) + chars.substring(i + 1);
                            findPerms(mystr + chars.charAt(i), newString);
                        }

               Collections.sort(permsList);

               for(int i=0; i<permsList.size(); i++) {
                    System.out.print(permsList.get(i) + " ");
               }
       }
}

如果我输入一个字符串"玩具",我得到:

玩具tosy tyos tyso tsoy tsyo otys otsy oyts oyst osty osyt ytos ytso yots yost ysto ysot stoy styo soty soyt syto syot

我究竟做错了什么.我怎样才能按字母顺序排列它们？谢谢!

Answer 1

您正在从递归方法中调用您的排序例程,该方法在完全填充之前查找String的所有排列.

import java.util.*;

public class permutations {

        public static void main(String args[]) {
            Scanner s = new Scanner(System.in);
            System.out.print("Enter String: ");
            String chars = s.next();
            List<String> myList = new ArrayList<String>();
            findPerms(myList, "", chars);

            Collections.sort(myList);

            for(int i=0; i<myList.size(); i++) {
               System.out.print(myList.get(i) + " ");
            }

        }

        public static void findPerms(List<String> permsList, String mystr, String chars) {

            if (chars.length() <= 1)
                permsList.add(mystr + chars);    
            else
            for (int i = 0; i < chars.length(); i++) {
                String newString = chars.substring(0, i) + chars.substring(i + 1);
                findPerms(permsList, mystr + chars.charAt(i), newString);
            }

       }
}