hello, is there currently a tool which can convert C# codes to Java (for example to be used in NetBeans)?

I doubt it, but won't kill you to look for it, I guess.

May I ask why? If you just need portability you could try compiling it with MonoDevelop (supports Linux, Mac OSX and Windows). Never really used it personally though...

I would like to know the equivalent code which results when moving a program from C# to Java

The languages are very similar, but the APIs are completely different. Converting the syntax (with a few specific exceptions) is no big deal, but mapping/converting the APIs would be a massive task.

There are a number of tools available. CS2J is an off-line converter. It uses translation templates to guide the conversion of .Net APIs to Java.