java实现反转字符串的指定位置

package com.atguigu.java1;

import java.util.Scanner;





public class fanZhuan {
    public static void main(String[] args) {
        String s2 = "abcdefghijklmn";
        fanZhuan f = new fanZhuan();
        System.out.println(f.reverse(s2));
    }

        public String reverse(String s){
            String s1 = "";
            Scanner scan = new Scanner(System.in);
            System.out.println("请输入你想要改变字符串的首位置");
            int start = scan.nextInt();
            System.out.println("请输入你想要改变字符串的末位置");
            int end =scan.nextInt();

            for(int j = 0;j < start;j++){
                s1 += s.charAt(j);
            }
            for (int i = end - 1;i >= start;i--) {
                s1 += s.charAt(i);
            }
            for(int k = end;k < s.length();k++){
                s1 += s.charAt(k);
            }

            return s1;
        }

}