moving the characters in a text string a specified number of positions

Question

I am new in programming and I am trying to write a program that moves the characters in a text string a specified number of positions.

The program must include a method whose inputs will be a text string (type String) and the number of positions (type int). The output will be a string with characters shifted.

For example, moving 4 positions:

rabbit eats a carrot
it eats a carrotrabb

Now I have this partial code. I can erase first characters but I don't know how to put them to the end of this text. How can i make it?

public static void main(String[] args) {
    System.out.println("enter the text: ");
    Scanner cti = new Scanner(System.in);     
    String a = cti.nextLine();
    System.out.println("enter number of positions= ");
    int b = cti.nextInt();
    char firstLetter = a.charAt(0);
    b--;
    a = a.substring(b); 
    String m = a + firstLetter ;
    System.out.println("now it is "+ m);
}

Answer 1

If you use regex, it's just one line:

return str.replaceAll("^(.{" + n + "})(.*)", "$2$1");

Answer 2

import java.util.*;
public class JavaApplication5 {
    public static void main(String[] args) {
        System.out.println("enter the text: ");
       Scanner cti = new Scanner(System.in);     
       String a = cti.nextLine();
        System.out.println("enter number of positions= ");
        int b = cti.nextInt();
       String firstPart = a.substring(0,b);   // line 1
       b--;
       a = a.substring(b); 
       String m = a + firstPart ;             // line 2
        System.out.println("now it is "+ m);
    }
    
}

See the changes above in statement marked with comment line 1 and line 2.

In line 1, we are getting the first part of string and in line 2, adding at the end of second string part.