DrJava is an integrated development environment (IDE) for writing, compiling and debugging programs in the Java programming language. This documentation is focused only on getting DrJava running, other documentation is available at the end of this post.
DrJava works with JDK 5, 6 and 7 according to the release notes.
Answer two short questions:
Is your operating system Windows, Mac or Linux?
Is your operating system 32- or 64-bit?
Windows and Linux users can visit Oracle to download a version of Java SE 6/7 JDK for your specific operating system. Both 32- and 64-bit versions are available for nearly every platform.
Mac users must register as a developer with Apple to get the JDK for Mac. If you already have an Apple ID this should not be a problem. The product named Java for OS X 2013-004 Developer Package is what you probably want. But, you should also check out the docs from Oracle. Or you can just download from the same Java SE 6/7 JDK link as Windows and Linux from above.
Also, if you open Terminal on the Mac and type “javac”, you will receive the message: No Java runtime present, requesting install.
Which will then ask if you want to find an appropriate runtime.
Install the Java SE JDK on your operating system according to the manufacturers recommendations.