剑指Offer之左旋转字符串

 1 public class Solution {
 2     public String LeftRotateString(String str,int n) {
 3         if(str.length()==0||n<0)
 4             return "";
 5         StringBuilder sb=new StringBuilder(str.substring(0, n));
 6         StringBuilder sb1=new StringBuilder(str.substring(n, str.length()));
 7         sb1.append(sb);
 8         return sb1.toString();
 9         
10     }
11 }