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Java is a popular programming language written by Sun Microsystems. It's an object-oriented language that runs inside a "virtual machine" which, at least in theory, allows code to run on many different machines. Sun calls this "Write once, run anywhere", and in practice it actually works reasonably well, although it took years for this to happen.

Java is extremely popular in commercial software development - it's dominant in the area that I work in: operations support software for communications companies. It's not at all popular in the Free Software community because it's a proprietary product owned and controlled by Sun.

The Java home page is http://java.sun.com/; you can download a developer kit or run-time from there. Java per se is a proprietary product, but there are many free projects that aim to provide all (or part) of the Java environment as Free Software. http://www.dwheeler.com/java-imp.html lists many of those projects.

Books

Bruce Eckels Thinking in Java

Nutshell

Development Tools

building: ant - "like make only without make's wrinkles"

modelling: argouml - a UML modelling tool that can generate Java skeletons.

debugging: jswat

database access: isql, squirrelsql

Infrastructure

tomcat - servlet engine, jboss - j2ee container, openejb - ejb container, avalon - server framework, maverick - presentation framework

Libraries

trace logging: log4j

Misc

Here's a cute hack to enable token substitution in java property files: http://www.sys-con.com/java/source.cfm?id=1228

Using Java on Debian GNU/Linux

When I tried to run Sun's JDK 1.3.1 on Debian Sid (in March 2002) I got the following error: /home/tcabot/local/Linux/jdk/bin/i386/native_threads/java: error while loading shared libraries: libstdc++-libc6.1-1.so.2: cannot open shared object file: No such file or directory. This can be solved by linking to the existing libstdc++, i.e. ln -s /usr/lib/libstdc++-libc6.2-2.so.3 /usr/lib/libstdc++-libc6.1-1.so.2.

Java is a proprietary language (controlled by Sun) but there are a few Free implementations of the compiler, JVM, and class libraries. If you're running a new version of Debian you can apt-get gcj and kaffe.

$ gcj -C HelloWorldApp.java
$ kaffe -addclasspath . HelloWorldApp

-- TobyCabot - 28 Dec 2001-16 May 2002