java之左旋转字符串介绍

public class Test_21 {
 public static void main(String[] args){
  StringBuilder str = new StringBuilder("abcde");
  int index =5;
  System.out.println(LeftTurn(str,index));
 }
 public static String LeftTurn(StringBuilder sb,int index){
  int strlen = sb.length();
  if(sb !=null&&index>=0&&index<=strlen){
   int firststart = 0;
   int firstend = index-1;
   int secondfirst = index;
   int secondend = strlen-1;

   

    
    ReverseString(sb,firststart,firstend);
    ReverseString(sb,secondfirst, secondend);
    ReverseString(sb,firststart,secondend);

   
   return sb.toString();
  }
  return null;

 }
 public static void ReverseString(StringBuilder str,int begin, int end){

  while(begin<=end){
   char temp = str.charAt(begin);
   str.setCharAt(begin, str.charAt(end));
   str.setCharAt(end, temp);
   begin++;
   end--;
  }
  System.out.println(str);
 }

}