2.1 Apple JVM Basics

First, make sure you have a Java Virtual Machine (JVM). Open up the Terminal application, type java -version, and you'll see the following message (or something similar):

java version "1.3.1"
Java(TM) 2 Runtime Environment, 
    Standard Edition (build 1.3.1-root-020219-20:07)
Java HotSpot(TM) Client VM (build 1.3.1, mixed mode)

This message indicates that your JVM is set up and working, and that may seem like all you need to know. However, there is much more to a JVM than the ability to fire up a Java process. For starters, Apple preinstalls the JVM in a specific location, automatically including a number of additional classes. These classes number in the hundreds and add Apple-specific functionality to the core Java distributions.

In this section we'll look at Apple's JDK 1.3.1 installation, which is included with all Mac OS X 10.1 systems and beyond. The JDK 1.4.1 release is available for download via Apple's Software Update feature or http://www.apple.com/macosx/downloads. It will install only on Mac OS X Version 10.2.3 or later.

The Swing settings are also unique to the Apple JVM: the default look and feel corresponds to the Aqua user interface, which has quite an effect on your graphical applications. Apple also added hardware acceleration (for JDK 1.3) and implemented a shared memory model for reducing the overhead of running multiple Java applications. Although you've got the same basic JVM as on a Unix, Linux, or Windows platform, you should pay attention to some additions and differences.