Java™ Application Development on Linux - Dator

6.3 How the IBM JDK Differs from the Sun JDK1756.3.1 PerformanceIBM’s Java implementation appears to run most code faster than the Sun implementation.Benchmarking something as complex as a Java Virtual Machineis well beyond our scope here (and, in fact, coming up with a benchmark thatwill actually predict how much faster your application will run on one environmentversus another is practically impossible). Nonetheless, we have seen somefairly dramatic performance improvements when running Java applicationsunder the IBM JVM—improvements on the order of 50%–100%.It is interesting to note that it does not matter which Java SDK producedthe bytecode files. We see these improvements when the compiled classes arerun, no matter which compiler (IBM’s or Sun’s) was used to produce them.This suggests that it is some combination of a faster virtual machine and/or abetter Just-In-Time compiler (JIT) that gives IBM’s runtime its apparentperformance advantage.For the most part, we use the Sun development kit and runtime, simplybecause Sun’s is the definition of Java. But if execution speed is proving to becritical for your application, consider the IBM Java runtime. You may see somespeed advantages.6.3.2 Differences in the CommandsYou will notice a few differences. For example, there is both a java and a javaw.Both invoke the Java runtime. The former has the Java console interface, thelatter does not. For our purposes, this does not matter. The IBM Java SDKcomes with an Object Request Broker Daemon (orbd) for CORBA/IIOP whilethe Sun SDK does not. Again, for our purposes this doesn’t matter.For the bulk of the utilities, the differences are so slight that you can usethe Sun documentation for the IBM tools.6.3.3 IBM ClassesIBM’s Eclipse project (which we begin to cover in Chapter 10) provides a largeGUI API library called SWT. We won’t go into that here; it is covered inChapter 17. Of more immediate interest is IBM’s enhanced BigDecimal class(com.ibm.math.BigDecimal) which addresses a lot of deficiencies in Sun’simplementation of decimal arithmetic. We will be using the standard Java classin our book (as it is the same for all development kits we cover), but you mightwant to take a look at IBM’s FAQ document on their enhanced BigDecimal