Each and every, if you are their owner (or the system-administrator), and they are not in use in the moment.
Can you find those duplicate files? If you can find them then you can delete them. If you need a tool who can help you to find those files, you can go to cisdem and click DuplicateFinder. This application will help you.
Java does not require header files like C/C++.
'.java' files contain java source code. One can access these files on windows by using 'notepad'.
No, rebooting does not delete your files.
Java doesn't use header files.
Those files have the extension .java
Without Java files, we wouldn't be able to program in Java. And some of us find Java to be an important programming language.
Java source files have the .java extension, compiled Java class files have the .class extension.
If you run Install then Repair it shouldn't delete files in "My Documents" (at least it didn't when I did it recently). If you run Install then Install it will delete the files.
no is there a software to delete it
You need a decompiler to convert class files to java source files. JAD is a Java Decompiler that can do it for you.
You can patch the phone with a VKP patch according to your firmware to make the files visible. I used the "java access to tpa" patch which is easily availble with a google search. The "internal" files are actually hidden in the file manager, so you'd have to get a app to view and manage the files also, I use MobyExplorer. With that, and the patch, you can play around with internal files and delete them or modify them to your liking.