"To develop Java software you need a development tool.
The Java development kit freely available from JavaSoft provides a command level compiler for developing Java software.
You use your favorite text editor to write the Java code and compile it using the "javac" command.
To test a Java application you just execute it at command level.
To test an applet you would use the appletviewer available in the JDK to launch an HTML document that specifies the applet tag and your applet.
Those who want a friendlier development environment should consider a Java software tool like a IDE, a RAD or a development tool.
An IDE (integrated development environment) provides a graphical user interface for Java programmers to build, debug, and test Java software.
A development tool allows for the quick development of Java software using a graphical user interface with a drag-and-drop approach.
A development tool offers prebuild components that the user pieces together to build software.
A RAD is a rapid application development tool that combines an IDE, a development tool and additional software development functions
into a comprehensive product for developing Java software." (Web Developer's Virtual Library)