Java Network Programming (3rd ed) [Electronic resources] نسخه متنی

Java Versions

Java's network classes
have changed a lot more slowly since Java 1.0 than other parts of the
core API. In comparison to the AWT or I/O, there have been almost no
changes and only a few additions. Of course, all network programs
make extensive use of the I/O classes and many make heavy use of
GUIs. This book is written with the assumption that you and your
customers are using at least Java 1.1. In general, I use Java 1.1
features like readers and writers and the new event model freely
without further explanation.

Java 2 is a bit more of a stretch. Although I wrote almost this
entire book using Java 2, and although Java 2 has been available for
most platforms for several years, no Java 2 runtime or development
environment is yet available for MacOS 9. It is virtually certain
that neither Apple nor Sun will ever port any version of
Java 2 to MacOS 9.x or earlier, thus effectively locking out 60% of
the current Mac-installed base from future developments. This is not
a good thing for a language that claims to be "write
once, run anywhere." Furthermore,
Microsoft's Java
virtual machine supports Java 1.1 only and does not seem likely to
improve in this respect for the foreseeable future. Thus, while I
have not shied away from using Java 2-specific features where they
seemed useful or convenientfor instance, the ASCII encoding
for the InputStreamReader and the
keytool programI have been careful to
point out my use of such features. Where 1.1 safe alternatives exist,
they are noted. When a particular method or class is new in Java 1.2
or later, it is noted by a comment following its declaration like
this:

public void setTimeToLive(int ttl) throws IOException // Java 1.2

To further muddy the waters, there are multiple versions of Java 2.
At the time this book was completed, the current release was the
"Java™ 2 SDK, Standard Edition, v
1.4.2_05". At least that's what it
was called then. Sun seems to change names at the drop of a marketing
consultant. In previous incarnations, this is what was simply known
as the JDK. Sun also makes available the
"Java™ 2 Platform, Enterprise
Edition (J2EE©)" and
"Java™ 2 Platform, Micro Edition
(J2ME©)". The Enterprise Edition is
a superset of the standard edition that adds features like the Java
Naming and Directory Interface and the JavaMail API that provide
high-level APIs for distributed applications. Most of these
additional APIs are also available as extensions to the standard
edition, and will be so treated here. The Micro Edition is a subset
of the standard edition targeted at cell phones, set-top boxes, and
other memory, CPU, and display-challenged devices. It removes a lot
of the GUI APIs programmers have learned to associate with Java,
although surprisingly it retains many of the basic networking and I/O
classes discussed in this book. Finally, when this book was about
half complete, Sun released a beta of the
"Java™ 2 SDK, Standard Edition,
v1.5". This added a few pieces to the networking
API, but left most of the existing API untouched. Over the next few
months Sun released several more betas of JDK 1.5. The finishing
touches were placed on this book and all the code tested with JDK 1.5
beta 2. You shouldn't have any trouble using this
book after 1.5 is released. With any luck at all, discrepancies
between the final specification and what I discuss here will be quite
minor.

To be honest, the most annoying problem with all these different
versions and editions was not the rewriting they necessitated. It was
figuring out how to identify them in the text. I simply refuse to
write Java™ 2 SDK, Standard Edition,
v1.3 or even Java 2 1.3 every time I
want to point out a new feature in the latest release of Java. I
normally simply refer to Java 1.1, Java 1.2, Java 1.3, Java 1.4, and
Java 1.5. Overall, though, the networking API seems fairly stable.
Java 1.1 through Java 1.3 are very similar, and there are a few only
major additions in Java 1.4 and 1.5. Very little of the post-1.0
networking API has been deprecated.