输出字符串的所有排列

 1 import java.util.ArrayList;
 2 import java.util.HashSet;
 3 import java.util.Scanner;
 4 
 5 public class RecursionPermutation {
 6     public static ArrayList<String> result = new ArrayList<String>();
 7     public static HashSet<String> set = new HashSet<String>();
 8     /**
 9      * 主函数入口
10      * @param args
11      */
12     public static void main(String[] args) {
13         System.out.println("请随意输入一串字符串：");
14         String inputString = new Scanner(System.in).next().toString();
15         ArrayList<String> result = Permutation(inputString);
16         for (int i = 0; i < result.size(); i++) {
17             System.out.println(result.get(i));
18         }
19     }
20 
21     /**
22      * 递归函数主入口
23      * @param str
24      * @return
25      */
26     public static ArrayList<String> Permutation(String str) {
27         if (str == null || str.length() == 0)
28             return result;
29         else
30             Permutation(str, 0, str.length() - 1);
31         result.addAll(set);
32         return result;
33     }
34 
35     /**
36      * 递归条件函数
37      * @param str
38      * @param start
39      * @param end
40      */
41     public static void Permutation(String str, int start, int end) {
42         char[] array = str.toCharArray();
43         String r = null;
44         if (start == end) {
45             r = String.valueOf(array);
46             set.add(r);
47         } else {
48             for (int i = start; i <= end; i++) {
49                 char tmp = array[start];
50                 array[start] = array[i];
51                 array[i] = tmp;
52 
53                 Permutation(String.valueOf(array), start + 1, array.length - 1);
54 
55                 tmp = array[start];
56                 array[start] = array[i];
57                 array[i] = tmp;
58             }
59         }
60     }
61