Week 11 Lab – Printing a String Backwards

Maximum Points = 10

Printing a string backwards can be done iteratively or recursively. To do it recursively, think of the following specification:

 

If s contains any characters (i.e., is not the empty string)

 

·       print the last character in s

·       print s' backwards, where s' is s without its last character

 

File Backwards.java contains a program that prompts the user for a string, then calls method printBackwards to print the string backwards. Save this file to your directory and fill in the code for printBackwards using the recursive strategy outlined above.

 

 

// ******************************************************************

//   Backwards.java

//

//   Uses a recursive method to print a string backwards.

// ******************************************************************

import java.util.Scanner;

 

public class Backwards

{

 

    //--------------------------------------------------------------

    // Reads a string from the user and prints it backwards.

    //--------------------------------------------------------------

    public static void main(String[] args)

    {

      String msg;

      Scanner scan = new Scanner(System.in);

 

      System.out.print("Enter a string: ");

      msg = scan.nextLine();

 

      System.out.print("\nThe string backwards: ");

      printBackwards(msg);

      System.out.println();

    }

     

    //--------------------------------------------------------------

    // Takes a string and recursively prints it backwards.

    //--------------------------------------------------------------

    public static void printBackwards(String s)

    {

 

      // Fill in code

 

    }

}

 

(Due before end of the day on Friday, April 1, 2011) Submit your .java files containing your program to the dropbox in WebCT.

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