Java newbie, GUI question
Hi there.
For a homework assignment I'm supposed to write an applet that tells whether or not a String input by the user is a palindrome. I think I have the logic worked out (and if I don't, I can fix that part myself), but this is my first GUI. The following compiles, but I keep getting an OutOfBounds exception (it says on line 38, which is where the variable indexTwo is defined) whenever the button is clicked. I'm not sure why; if it's just a little error or I need to approach it differently.
It's a little bit messy, I just want to make it work. Also, I originally had two classes and used a array, but the prof said the assignment should be one class per question and no arrays were needed (which I think is silly for a couple of the questions, but whatever).
Code:
// leading comments etc
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class PalindromeTest extends JApplet implements ActionListener {
private JTextField inputString;
private JButton theButton; //oh, and should I move this to the init() method?
private JLabel truthLabel;
public void init() {
truthLabel = new JLabel("Input your text and click the button.");
theButton = new JButton("Is it a palindrome?");
inputString = new JTextField(20);
theButton.addActionListener(this);
Container contentPane = getContentPane();
contentPane.setLayout(new FlowLayout());
contentPane.add(inputString);
contentPane.add(theButton);
contentPane.add(truthLabel);
}
public void actionPerformed(ActionEvent e) {
String strIn = inputString.getText();
String str = strIn.toUpperCase(); //possibly redundant?
boolean isPalindrome = true;
int indexOne = 0; //beginning of the string (index marker 1)
int indexTwo = str.length(); //ending of the string (index marker 2)
while (indexOne < indexTwo){
char charOne = str.charAt(indexOne);
char charTwo = str.charAt(indexTwo);
if (charOne != charTwo){ //exceptional case
isPalindrome = false;
break;
}
else {
indexOne += 1; //move the first marker to the right
indexTwo -= 1; //move the second marker to the left
}
} //end of the while loop
if (isPalindrome)
truthLabel.setText("That is a palindrome.");
else
truthLabel.setText("That is not a palindrome.");
}
}
