Java Reference
In-Depth Information
6.3.1
IBM's Java implementation appears to run most code faster than the Sun im-
plementation. Benchmarking something as complex as a Java Virtual Machine
is well beyond our scope here (and, in fact, coming up with a benchmark that
will actually predict how much faster
your
application will run on one environ-
ment versus another is practically impossible). Nonetheless, we have seen some
fairly dramatic performance improvements when running Java applications
under the IBM JVM—improvements on the order of 50%-100%.
It is interesting to note that it does not matter which Java SDK produced
the bytecode files. We see these improvements when the compiled classes are
run, 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 a
better Just-In-Time compiler (JIT) that gives IBM's runtime its apparent
performance advantage.
For the most part, we use the Sun development kit and runtime, simply
because Sun's is the definition of Java. But if execution speed is proving to be
critical for your application, consider the IBM Java runtime. You may see some
speed advantages.
Performance
6.3.2
You 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, the
latter does not. For our purposes, this does not matter. The IBM Java SDK
comes with an Object Request Broker Daemon (
orbd
) for CORBA/IIOP while
the 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 use
the Sun documentation for the IBM tools.
Differences in the Commands
6.3.3
IBM's Eclipse project (which we begin to cover in Chapter 10) provides a large
GUI API library called SWT. We won't go into that here; it is covered in
Chapter 17. Of more immediate interest is IBM's enhanced
BigDecimal
class
(
com.ibm.math.BigDecimal
) which addresses a lot of deficiencies in Sun's
implementation of decimal arithmetic. We will be using the standard Java class
in our topic (as it is the same for all development kits we cover), but you might
want to take a look at IBM's FAQ document on their enhanced
BigDecimal
IBM Classes
