LAB 36 – Creating and Modifying Text (part 1)

Lab Exercises

Topics

n To manipulate structured text, such as a delimited string.

n To manipulate strings

n To use the swing class JOptionPane

Exercises

12.2 Strings: Character Sequences

i) Open a new file in Dr. Java and type in the following program:

//********************************************************************
//  PalindromeTester.java       Author: Lewis/Loftus
//
//  Demonstrates the use of nested while loops.
//********************************************************************
 
import java.util.Scanner;
 
public class PalindromeTester
{
   //-----------------------------------------------------------------
   //  Tests strings to see if they are palindromes.
   //-----------------------------------------------------------------
   public static void main (String[] args)
   {
      String str, another = "y";
      int left, right;
 
      Scanner scan = new Scanner (System.in);
 
      while (another.equalsIgnoreCase("y")) // allows y or Y
      {
         System.out.println ("Enter a potential palindrome:");
         str = scan.nextLine();
 
         left = 0;
         right = str.length() - 1;
 
         while (str.charAt(left) == str.charAt(right) && left < right)
         {
            left++;
            right--;
         }
 
         System.out.println();
 
         if (left < right)
            System.out.println ("That string is NOT a palindrome.");
         else
            System.out.println ("That string IS a palindrome.");
 
         System.out.println();
         System.out.print ("Test another palindrome (y/n)? ");
         another = scan.nextLine();
      }
   }
}

ii) Test your program (radar; able was I ere I saw elba; a man, a plan, a canal, Panama).

iii) Modify the main method by

a. Add import javax.swing.JOptionPane;

b. Change the while loop to a do-while using a JOptionPane

i. Declare an integer variable again to hold the result of the pop-up

ii. Replace         System.out.print ("Test another palindrome (y/n)? ");

with      again = JOptionPane.showConfirmDialog (null, "Do Another?");

iii. Replace the condition in the while with again == JOptionPane.YES_OPTION

c. Replace the input and prompt:

i. Replace         System.out.println ("Enter a potential palindrome:");

    str = scan.nextLine();

                                    with      str = JOptionPane.showInputDialog ("Enter a potential palindrome:");

d. Replace the results:

i. Replace      the two remaining System.out.println with

JOptionPane.showMessageDialog (null, "That string is NOT a palindrome.");

QUESTIONS:

Submit the PalindromeTester.java files through the DropBox in WebCT.