Why is the value of my variable always -1?

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private void btnCalculateMouseClicked(java.awt.event.MouseEvent evt) {                                          
        String hexNumber;
        int decNumber = 0;
        int counter;

        hexNumber = txtHexNumber.getText();

        for (counter = (hexNumber.length() - 1); counter >= 0; counter--);
        {
            System.out.println(counter);
        }
        txtDecNumber.setText(decNumber + "");
    }

It doesn't care how long the String hexNumber is, the value of counter is always -1!
But I don't understand why!

What I have tried:

I tried to run the code in the single-step mode but I couldn't find the problem.

Posted 28-Dec-16 6:07am

OnLearn

Updated 28-Dec-16 9:02am

Patrice T

v2

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[no name] 28-Dec-16 12:32pm

Take the semi-colon off of the end of your for line.

2 solutions

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Peter Leow · Accepted Answer · 2016-12-28T06:38:00

Solution 1

The culprit is that semi-colon that terminates your loop:

for (counter = (hexNumber.length() - 1); counter >= 0; counter--);

Posted 28-Dec-16 6:38am

Peter Leow

Updated 28-Dec-16 6:40am

v2

Comments

OnLearn 28-Dec-16 12:43pm

Thank you soo much! That are the little mistakes, which you won't find in hours!

Peter Leow 28-Dec-16 13:04pm

You are welcome.

Patrice T · Accepted Answer · 2016-12-28T09:01:00

The problem is the semi at the end of this line.

C++

for (counter = (hexNumber.length() - 1); counter >= 0; counter--);

You should learn to use the debugger as soon as possible. Rather than guessing what your code is doing, It is time to see your code executing and ensuring that it does what you expect.

Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.