Feel like a genius. Answer my pathetic looping question.

[KevinC]

Hey everyone. New to the forum. I want to get good at Java but it is painstaking so far.

Here is my question.
This is a tutorial for a command line application. I try to do all my exercises in Netbeans because I like GUIs.
Could someone be kind enough to tell me why this loops endlessly, and possibly how to fix it?

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    
    // Generate a random number to be guessed
    int number = (int)(Math.random() * 101);
    
    // Get the integer from the textbox
    int guess = Integer.parseInt(userInput.getText());
            
    while (guess != number) {
          
    if (guess == number)
        answerOutput.setText("Yes, the number is " + number);
    else if (guess > number)
        answerOutput.setText("Your guess is too high");
    else
        answerOutput.setText("Your guess is too low");
    // End of loop     
    }

[Fubarable]

Where do you change the value held by the guess variable inside of the loop?

Oh, and welcome to the java-forums!

In a minute, I'll add [code] [/code] tags to your code,... hang on!

[KevinC]

I read you sentence about 10 times, and I am confused.

I didn't think the value of guess would need to change...

Perhaps I should come back after I do more research.

I appreciate you helping me with this though.

[Fubarable]

I read you sentence about 10 times, and I am confused.

I didn't think the value of guess would need to change...

Let's simplify. Say you have this bit of code:

int x = 0;

while (x == 0) {
   System.out.println("x is 0 still");
}

Since x never changes inside of the loop, it has no chance of changing to a non-zero value, and the loop will never end. Contrast that with this loop:

int x = 0;

while (x == 0) {
   System.out.println("x is 0 still");
   x = 3;
}

Now x changes inside of the loop to 3, and the loop can exit. So the sentinal variable (in this case, x) must change inside of the loop for the code's behavior to change (in this case, in order to exit the loop).

Clear as mud?

[KevinC]

Sweet. I got it.
Thanks for your help good sir.
I hate to be a bother with such trivial questions.

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    
    // Generate a random number to be guessed
    int number = (int)(Math.random() * 101);
    
    // Get the integer from the textbox
    int guess = -1;   
            
    while (guess != number) {
         guess = Integer.parseInt(userInput.getText());
    if (guess == number)
        answerOutput.setText("Yes, the number is " + number);
    else if (guess > number)
        answerOutput.setText("Your guess is too high");
    else
        answerOutput.setText("Your guess is too low");
    // End of loop     
    }

[Fubarable]

Sweet. I got it.
Thanks for your help good sir.
I hate to be a bother with such trivial questions.

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    
    // Generate a random number to be guessed
    int number = (int)(Math.random() * 101);
    
    // Get the integer from the textbox
    int guess = -1;   
            
    while (guess != number) {
         guess = Integer.parseInt(userInput.getText());
    if (guess == number)
        answerOutput.setText("Yes, the number is " + number);
    else if (guess > number)
        answerOutput.setText("Your guess is too high");
    else
        answerOutput.setText("Your guess is too low");
    // End of loop     
    }

You'll still never leave that loop because of a threading issue. Since the loop ties up the event thread, the GUI will become unresponsive leaving you no way to change the value inside of your JTextField.

[KevinC]

I will re-visit your statement when I am more knowledgeable. I have a long journey ahead of me with this stuff.