What is JDK?
JDK referred as Java Development Kit is used to develop various types of application in JAVA.
Portable means the code which can run anywhere you want.
The portable JDK is also similar to that as we use JDK without actually installing it on our system. Check out the following video in Hindi language which explains you all the process in detail.
Some useful links:
To download jdk latest version: http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
To download 7-zip: 7 Zip download