What is Java Development kit (JDK)

The java development kit (JDK) is product of sun Microsystems used to develop java software and is an extended subset of a java software development kit (SDK). JDK consists of the API classes, A java compiler, and the java Virtual Machine interpreter. JDK is used to compile java application and applet. JDK include tools for developing java applets and application.

A java software developments kit (SDK or "devkit") is a set of development tools that is used in developing application for certain software package, software framework, hardware platform  , computer system, video game, console , operating system, or similar platform. if J2SE 1.2 is used to develop application, then you are using the platform what's known as the Java 2 Platform. Installation and configuring of  Java