JAVAs for NetRexx

You may already have a JAVA directory on your machine, put there by Netscape or Internet Explorer. This will be an execution environment, insufficient for creating programs. To develop programs (either directly in JAVA or with NetRexx) you need something called a JDK - Java Development Kit.

There are various levels of JDK for various operating systems and there are two current levels of NetRexx. To checkout the NetRexx levels link to the NetRexx site (Beware sites which are "mirror sites" to this one; they may not be up-to-date.) You will find that almost any JDK will do for non-interpreted NetRexx. But if you are a Rexx person you will want to be trying the interpreter version, which needs JAVA 2 (1.2).

This notation arises because originally the JDKs had a three part version number, 1.1.n, and at the same time as the second part went from 1 to 2, the architecture and implementation were redesignated from JAVA to JAVA 2. (This does not apply to the language - there is no JAVA 2 language.) So a JDK version number, that starts 1.1, will not be JAVA 2, anything else will be. As of mid-2000, this means 1.2 and 1.3 levels are JAVA 2. (1.2.0 is the same as 1.2, 1.3.0 the same as 1.3)

The NetRexx site gives us links to sources of Java JDKs and from these we can (eventually/probably) arrive at lists of downloads. Here are the ones for Sun and IBM (Where they both offer for the same operating system it is likely the Sun one will be a later version, the IBM one a better performer.)

You will see that only Sun is offering JAVA 2 today (June 2000). That means that if you want interpreted NetRexx on Warp, or VM, or S/390 you are out of luck. However, the IBM look-ahead site says that you may not have to wait long.

A JDK is big, typically 30meg or so. You will want the specifications of what you are getting as well, another 25meg or so (from the Sun site). The JDK for Windows comes as an EXE file that, when you run it, installs the JDK. There will be another 30meg needed for what is installed. The download site provides detailed installation instructions. (Optionally, the EXE can be deleted after this to recover disk space.) The download site may offer you an Integrated Development Environment (IDE) analogous to the Object Rexx development environment - this is not what you want since it is for Java, not NetRexx.

All the disk spaces used for Java should be in a format that supports long file names - so, for example, a non-HPFS Warp partition will not do.

NetRexx executes on Java so, whatever the operating system, once you have the Java JDK you only need a copy of NetRexx and that copy will be the same bytes whatever the operating system. (Although the documentation will have to be in the appropriate ASCII or EBCDIC) However, there is a system dependency in the process of acquiring a copy of NetRexx. The copy will come compressed; Unix-type systems expect a "tar" format and personal computer type systems expect a "zip" format. So you need to download the appropriate version and you need a program to decompress it with. There are detailed instructions at the download site. By comparison with Java, the extra space required for NetRexx is small - less than 1meg to download. There are some testcases to check successful installation of the NetRexx compiler, and the installation instructions tell you how to use them. The README for the interpreter gives a simple test that the interpreter is working.

If you would like to share your experiences in getting to this first stage of evolving from a Rexx programmer to a Rexx&NetRexx programmer ("I gave up because...":-) then you might email - if a pattern emerges then I will summarize it for this web site.

Brian Marks