# Java: Software Development Kit

The most popular non-IDE (see IDEs) Java compiler is Sun's Software Development Kit (SDK) (aka the Java Development Kit (JDK)). It's free, and does a good job. The only problem is that the compiler is only a compiler - no editor and no graphical user interface. It must be used from the DOS command line window, or with a program editor (eg, TextPad, jEdit, ...) which have an interface to the compiler to give some of the benefits of an IDE.

## Free Download

Download from java.sun.com. There are three editions - get the "standard edition". Sun has major problems getting the names right, so this is still called Java 2 some places altho it is Java 5 in others.

- J2SE - Java 2 Standard Edition - You want this.
- J2ME - Java 2 Micro Edition - This is for phones, PDAs, etc.
- J2EE - Java 2 Enterprise Edition - You don't want this unless you're doing Java client server programming, and even then, you probably don't need it.

## Installation

Installing the JDK is easy (at least in Windows).

## CLASSPATH

Both the Java compiler (javac) and Java runtime (java) need to know where to find class files. The standard Java packages used in imports are not a problem, but the file system paths of other classes must be specified. The operating system (eg, Windows) maintains environment variables that supply information to the programs on request. The `CLASSPATH` variable is a semi-colon separated list of directories or `jar` files to to search in. In addition to non-Sun libraries that are used, the current directory (".") is specified so that classes a user is working on will be found.