i know about python, ruby, perl etc.. but is java a really open source programming language? because i searched on google too but didnt get proper answer. so asking here
Yes, or it will be eventually (there may still be some things they're working on replacing since they were used under licence). Sun committed to making it open source and you can download it from them. Check out OpenJDK.
A programming language isn't in it self open source or not, but an implementation of it might be. Yes, there are open source implementations of Java. Sun's Java implementation (the most popular one), is one of them.
The "official" SUN implementation of the language itself is not, but there is a community-driven process (not sure how well it works) for suggestions to improve the language - the Java Community Process. There are also open implementations of the Java development tools and runtime, such as OpenJDK.
OpenJDK after you download it in a src folder you have windows,solaris,share,linux in the share folder, you can find classes. There you can see the source code of, lets say JButton.
The phrase "Java Programming Language" refers to the specification as provided by Sun (now oracle). Sun provides a reference implementation of Java Virtual Machine and Java Compiler. Both of which are not open source (at least not fully like say Python).
However OpenJDK for example is a complete open-source implementation of JAVA programming language. There might be more as well.
Most of the programmers think of Java as a programming language provided by Sun. I think Sun only provides the language specification implementation can be done by anyone under any license.