OpenJDK

OpenJDK is an free implementation of Java for Linux, Solaris and Windows.^[1] There is also OpenJDK for BSD^[2]. Several BSD and Linux distros carry packages of OpenJDK.

OpenJDK can compile and run Java programs. OpenJDK 6 implements Java 6, while OpenJDK 7 is a preview of future Java 7.

Usage

OpenJDK is a set of command-line tools. If OpenJDK is installed in /usr/local/jdk-1.7.0, then /usr/local/jdk-1.7.0/bin needs to be added to the PATH environment variable. The two most important tools are the javac compiler, and the java runner.

This example program would compute 12 - 4.

/* TwelveMinusFour.java */
public class TwelveMinusFour {
	public static void main(String[] args) {
		System.out.println(12 - 4);
	}
}

One can compile this program with javac, and run it with java.

$ javac TwelveMinusFour.java
$ java TwelveMinusFour
8

References

[1] OpenJDK Build README: Minimum Build Environments

[2] OpenJDK: BSD Port Project

[1]

[2]