go here and load the version with JAVA

http://processing.org/download/

[Edited]

is it really necessary to install processing and java for a stand-alone processing app?

java needs to be installed for a processing app to run (created via export -> export application).

so,just installing JRE should be enough.right?

As said, there is a version of Processing (for Windows) coming with Java. You haven't said what is your system.
And, unless it changed, Processing needs a full JDK, because it uses the Java compiler. The JRE is enough to run exported sketches (already compiled).