打印字符串的全排列

public class Pailiezuhe {public static void dayin(char[] s,int st){if(s==null||s[0]==' '){return;}int start = st;int end = st;if(start==s.length){   for(int i=0;i<s.length;i++){   System.out.print(s[i]);   }   System.out.println();}for(;end<s.length;end++){char temp = s[start];s[start] = s[end];s[end] = temp;dayin(s,st+1);           char temp1 = s[start];s[start] = s[end];s[end] = temp1;}}public static void main(String[] args) {char[] s = {'a','b','c','d'};//char[] s = {' '};dayin(s, 0);}}