public class Solution {public String LeftRotateString(String str,int n) {if(str==null||str.length()<n){return str;}StringBuilder sb = new StringBuilder();//左移几位,就抽取一个长度为几的字符串String substring = str.substring(0, n);String substring1 = str.substring(n, str.length());//将字符串进行拼接,因为是左移,就把后面的字符串放到前面,将要移...