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Move characters in a text string with a specified number of positions

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

The program must include a method, the input of which will be a text string (type String) and number of positions (type int

). The result will be a string with displaced characters.

For example, moving 4 positions:

rabb it eats a carrot
it eats a carrot rabb

I now have this partial code. I can erase the first characters, but I don't know how to put them at the end of this text. How can i do this?

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);
}
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5 answers 


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);
    }
    
}
Run codeHide result




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

On line 1 we get the first part of the line and on line 2 we add at the end of the second part of the line.

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public String foo(String s, int n) {
    String s2 = s.substring(0, n);
    s = s.substring(n) + s2;
    return s;
}


you can put multiple checks on this like an empty string or n is less than s.length (), etc.

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If you are using regex, this is just one line:

return str.replaceAll("^(.{" + n + "})(.*)", "$2$1");
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Better to use the modulus operator to calculate the number of shifts. When the initial shift number is greater than the length of the string. Check it:

public String shift(String string,int n){
    int nshift = string.length() < n ? n%string.length() : n ;
    String a = string.substring(0,nshift);
    return string.substring(nshift) + a ;
}
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Another version. All work is mostly done in 1 line:

String result = new StringBuilder(a).delete(0, b).append(a.substring(0,b)).toString();

Anyway, the complete code is:

import java.util.*;
public class ShiftLetters {
    public static void main(String[] args) {
        System.out.print("enter the text: ");
        Scanner cti = new Scanner(System.in);     
        String a = cti.nextLine();
        System.out.print("Enter number of positions: ");
        int b = cti.nextInt();

        String result = new StringBuilder(a).delete(0, b).append(a.substring(0,b)).toString();

        System.out.println(result);
    }    
}

Also, you can be more precise with your indentation style to improve readability.

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