IBM Systems Magazine, Mainframe - January/February 2017 - SE48

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IMPORTANT TOOLS
Java is a viable alternative for system programmer batch utilities

ANDREW ROWLEY
Owner

As a systems programmer, from time to time you probably write small utility programs
to make your job easier. You might write them in REXX or even Assembler. But have
you considered Java*?
Java has become well accepted as an application programming language on z/OS*.
IBM's Java Batch Launcher and Toolkit (JZOS) also makes it simple to run Java in batch
and provides classes to access various system services. This makes Java a real alternative
for system programmer batch utilities.
Java has some major advantages over REXX and Assembler. Built-in libraries like
Java Collections simplify programming problems. Portable code means that samples
published on the internet for other platforms can be easily adapted to z/OS. Free
and open-source libraries provide solutions for common problems. As a result, many
problems are more easily solved in Java than other languages on z/OS.

Black Hill Software

Andrew Rowley has been
working with z/OS and its
predecessors since 1991 and
started Black Hill Software
in 2006.

Black Hill Software
211 Dana St.
Ballarat VIC 3350, Australia
Andrew Rowley
+61-3-5331-8201
info@blackhillsoftware.com
blackhillsoftware.com

Java Collections
The Collections Framework is possibly the most important tool in the Java toolbox.
Two of the most useful collections are the ArrayList and the HashMap. The ArrayList is
an array that resizes as required. The HashMap is a collection of items accessed by key.
HashMap simplifies all sorts of tasks. For example, when comparing two lists of items
with the same keys (e.g., catalog entries), you can store one list in a HashMap and then
compare items from the other list, with no dependency on the order of items. You can
also use a HashMap to accumulate statistics by key, which makes calculating group
totals simple-again with no requirement that the data be in order.
Other more specialized collections implement sets, queues and stacks as well as
other types of lists and maps.
Sample Code and Open Source Libraries
Whatever your problem, chances are that someone else has been there before-but
not necessarily on z/OS. The ability to use samples published for other platforms is a
great time saver. For example, sending email from z/OS through Gmail, with TLS and
user authentication took about 30 minutes to implement using samples posted on
the internet.
There are also free and open-source libraries providing more comprehensive solutions
to various common problems. Apache Commons and Google Guava are well-known
examples. Why not give Java a try, and see what problems it can solve for you?
For more information, Java on z/OS examples and a Java API for SMF data visit:
blackhillsoftware.com/java

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Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe - January/February 2017