import java.util.ArrayList;public class Test45 {//打印一个字符串的全排列public static ArrayList<String> permutation (String str) {ArrayList<String> res =  new ArrayList<>();if (str == null || str.length() == 0) {return res;}char[] chs = str.toCharArray();process1(chs, 0, res);return res;}public static void process1 (char[] str , int i , ArrayList<String> res ) {if (i == str.length) {res.add(String.valueOf(str));}for (int j = i; j < str.length; j++) {swap(str , i , j);process1(str , i + 1 , res);swap(str , i , j);}}public static void swap (char[] chs , int i , int j) {char temp = chs [i];chs[i] = chs [j];chs[j] = temp;}
}