Q:

which java version to install Windows x86,Windows x64 so that it will run on both 32 bit and 64 bit

when i go to download page of the java there are two version for java 
Windows x86 
Windows x64

How to find out which version is suitable for installation ? 

A:

If your OS is windows 32 bit then download Windows x86 version.  If your OS is windows 64 bit then download Windows x64 version. 
Java is platform independent.  If you use platform independent libraries when developing; Your app will run on both 32 and 64 bit.