I have installed jdk and eclipse. but I can't start progamming. When I start from menu> New> class, it shows at the top "Source folder name is empty."
Can anyone help me?
My operating system is win7 64bit

You need to create a Java Project first, then add classes to that.
If you're not experienced in Java I strongly advise you NOT to try to learn Eclipse at the same time - you are super-imposing two very large learning curves. Just use a programmer's editor (eg notepad+) and the JDK command line utilities until you have built up some Java skills.

Thank you. I know C and php. I did not know the trick to create java project first. It is working.

OK, well, have fun. You'll find lots of friendly people here to help you learn Java (and use Eclipse!).
Now your immediate problem is answered, please mark this thread "solved" for our knowledge base. Start a new thread for any new question. Thanks.