Mike Tango wrote:
I write java code since 3 years (at work), (Most of the time copy paste from internet/forum...)
Sometimes it works but I don't know why / sometime it doesn't work and don't know why either .....
I am a believer of never ever writing, even a single line of code, that you do not understand. Without an understanding of the code, you can't confirm, if what you did works for all cases, and/or if you introduced another bug.
Don't have a strong recommendation on what to do, except, you have three years of code, that some you don't understand. Perhaps it would be a good idea to go back and understand it?
You'll have to go back to the beginning. Get a book on Java and start going through it. Write lots of code. Ask questions here when you don't understand something.
There's no magic; it takes hard work. And it isn't going to get easier if you go on cobbling stuff together by copy/paste. I was just talking to someone the other day about "experienced Java developers" who can't write simple code. We don't hire them. You don't want to be that guy.