Mac OS X in a Nutshell

Chapter 10. Running Java Applications

Java is Sun Microsystems’ popular “write once, read anywhere” software technology, whose applications can run on many different operating systems without the need for porting (modifications may be necessary due to OS differences). Java is unusual specifically because a single compiled Java program can run as is on many different operating systems. It’s not the only portable programming language that Mac OS X ships with, though; Perl, for example, is an interpreted language, so a Perl program also can run on many different machines, since it’s compiled every time it’s run. Apple considers Java support among Mac OS X’s core features; Java is one of the four types of Aqua-environment applications (as listed in Section 2.4.2.1). This chapter describes the process of running Java programs on Mac OS X.

How Java Works

Like Classic applications, compiled Java applications must run in their own environment, as they’re not in a binary format native to Mac OS X. Launching a Java program also launches the Java environment program, known as a virtual machine , or VM. As its name implies, its an entirely software-based “computer” that runs within the confines of the real computer’s operating system, and is capable of executing Java programs. The interpreter—the one OS-specific part of any system’s Java installation—takes care of translating the running program’s Java commands into Mac-friendly system calls, all on the fly.

Tip

Mac OS X uses Sun’s Hotspot ...