Thread: When do I need debugger?

Hi everyone,Im a newby here,so happy to find such helpful place!

I was writing a java programming exercise,I was following the steps from the E-book

After Ive done every step and was sure there is no syntax problem showing,I started to run the applet

But it end up like this,which the number kept counting up:Unnamed.jpg

Then I copied the entire code from the E-book,it runs smoothly without any problem.
The result should look like this,its a moving pattern,I took screenshot:

Unnamed4.jpg

Ive done several time re-typing,checked each code-line over and over,they are indentical Im sure.

So what should I do when I reach such problem?Do I and how to debug thing like this?

Thanks so much

Please paste your code here to get us better understanding about the issue.

A sense of where to look for a problem in your source code when a program is not running correctly comes with the experience of being your own (and other's?) debugger. Debuggers may or may not - may not being more likely - find logic errors caused by typos in code that compiles and runs but doesn't run exactly correctly. A debugger can't look at what's on the screen and determine that the animation isn't happening or isn't correct.

I good IDE can provide several hints that there may be something amiss in the code by indicating that variables or methods exist but are never used, the use of improper operators, statements that end too early with a misplaced semi-colon, and others.

As trod suggested, post the code and describe what's wrong with the way it runs, and we'll do our best to point you towards the solution. Sometimes when staring at one's own code a person sees what they want to see, not what's really there, and typos are invisible. Or it's possible that the code is exactly correct and there's some other technical reason why you're not getting the desired results.

I might have run too many time program,eclipse got stuck,

I closed the eclipse and run again,re-wrote the code as iriginal pattern,then it works!