DrJava is a lightweight development environment for writing Java programs. It is designed primarily for students, providing an intuitive interface and the ability to interactively evaluate Java code. It also includes powerful features for more advanced users.

System requirements
  • Minimum SDK 1.6.0 Build 22 GA (2011-06-27)
  • Needs at least 1024x768 pixels.
  • Minimum 128 Mb memory.

DrJava on an eComStation machine with Open JDK

Installing DrJava
Download drjava-stable-20140826-r5761.jar (12,9Mb). Also download the manual drjava-stable-20140826-r5761-javadoc.zip. Create a folder (directory) "drjava". Copy the file "drjava-stable-20140826-r5761.jar" to the new created folder (directory). That's it.

The drjava.cmd file
DrJava works with a little tweaking in OpenJDK in OS/2-eCS. I have made a drjava.cmd file with the following contents;
@echo off
set path=[drive: java]\JAVA160\bin
set BEGINLIBPATH=[drive: java]\JAVA160\bin
[drive: drjava]
cd [drive: drjava]\drjava
java -Xmx512m -Xms128m -Duser.home=[drive: drjava]\drjava -jar drjava-stable-20140826-r5761.jar 2>drjava-bugs.txt
I use 2 separate folders (directories), one for Java and one for DrJava with the files created by this program. The references used in the cmd file;

  • [drive: java] = drive with Java
  • [drive: drjava] = drive with DrJava

should be replaced with real drive letters. Edit and save the file "drjava.cmd" from the distribution. This file is copied to the "drjava" folder (directory). Furthermore, different paths?, adjust according to your needs.
Create a new program object. Specify the path and file name: "[drive: drjava]\drjava\drjava.cmd". In the tabpage Session check the boxes "OS/2 window", "Running as an icon" and "Close Window to end program". In the tabpage General you can enter the name "DrJava". You find enclosed in the file a suitable OS/2 icon.

Parameters / options explained
  • The "-Xms128m" specify the initial size of the memory allocation pool.
  • The "-Xmx512m" indicates the maximum limit of the used memory.
  • The addition "2>drjava-bugs.txt" ensures that errors are saved in the file "drjava-bugs.txt". The 2 in "2>" is not a typo!
  • The specification "-Duser.home=[drive: drjava]\drjava" ensures that DrJava will save all necessary files in own directory instead of saving them in the home directory.

In the file you can find the above command file (all driveletters are set to C:) and an OS/2 DrJava icon: drjava-ecs.zip.

revision July 17, 2016