To develop java applications you need to set-up the Java platform. Followings are required:
• Java Development Kit (JDK),it’s a java development,running (deployment) environment and includes:
1. Java Runtime Environment (JRE),that contains Java Virtual Machine and base APIs such as about I/O,RMI…etc.
2. Development tools & APIs such as the Java compiler and Java launcher tools
You can refer to the site from Sun Microsystems below to download JDK installation package
http://java.sun.com/javase

• Integrated Development Environment (IDE),it’s a software tool to help programmer to edit source code,compile,interpret and debug. There are some remark Java IDEs such as Eclipse,NetBeans,JCreator…etc. The downloaded link below is for NetBeans:
http://www.netbeans.org/