Java JDK

It is a bundle of software that you can use to develop Java based applications.
Java Development Kit is needed for developing java applications.
JDK needs more Disk space as it contains JRE along with various development tools.
It includes JRE, set of API classes, Java compiler, Webstart and additional files needed to write Java applets and applications.

Below is Java JDK downloader...
http://www.oracle.com/technetwork/java/javase/downloads/index.html#jdk