This is essential if you want to run JUnit tests in the Eclipse IDE using Java 9. We recommend to install the support via Eclipse Marketplace because it is crucial that the Eclipse install, the Java 9 VM and the patch match. Eclipse is popular for Java application development (Java SE and Java EE) and Android apps. It also supports C/C++, PHP, Python, Perl, and other web project developments via extensible plug-ins. Eclipse is cross-platform and runs under Windows, Linux and Mac OS.

That’s the “Java version” you need to know. Downloading the JDK When working with Java, you need to distinguish two Java software package types: • JRE: The “Java Runtime Environment” is necessary to run Java application. You cannot, however, compile Java programs with just the JRE. • JDK: The “Java Development Kit” is required when you want to compile Java programs. The JDK includes the JRE, and also comes with Java’s source code. Remark: Eclipse comes with its own Java compiler. That’s why you don’t need to install a JDK to create Java programs with Eclipse.

Eclipse doesn’t ship with the Java source code though. That’s why we still need the JDK. The JDK for Mac OS X comes as “Java Developer Package”. You can download it here: You’ll need an AppleID to download the JDK.

Fortunately, it’s free but you still need to register it. (Tip: You can use the same you use in the iTunes Store.) After logging in, type “java developer package” in the search field (see screenshot). Make sure the you download the Java Developer Package matching your Java version.

In my case, this is “Mac OS X 10.7 Update 1”. Note: Don’t confuse “10.7” for Java 7. It’s still Java 6. (So don’t download a “10.6” version when you’re running Mac OS X Lion.) Then install the JDK. This will install the JDK under: /Library/Java/JavaVirtualMachines/ Note: There’s also the directory /System/Library/Frameworks/JavaVM.framework/. However, this directory seems to be deprecated. The Java source code will be located here: /Library/Java/JavaVirtualMachines/.jdk/Contents/Home/src.jar Check an already installed JDK To check whether you’ve already installed a JDK, check the list of installed updates (see ) for an entry called “Java Developer Package”.

Note: Unfortunately, the Java Developer Package listed in the list doesn’t have any (visible) version information attached to it. I’m not sure whether the JDK will be updated automatically when a new version becomes available. To check the actual Java version of the installed JDK, go to /Library/Java/JavaVirtualMachines/ and check whether a package called like “1.6.0_29-b11-402.jdk” can be found there. In this example, the Java version would be “1.6.0_29”. Using the JDK in Eclipse On Mac OS X, Eclipse provides an automatic way to determine the directory of the installed JDK.

Go to the Eclipse Settings and open Java –> Installed JREs. Then, by clicking on the Search. Button, would find the newly installed JDK. Unfortunately, there seems to be a bug in Eclipse Ingido (3.7 – and probably in earlier versions, too) that prevents this button from working correctly. Reduce pdf file size below 100 kb. Clicking on it doesn’t do anything when there’s already one (and only one) JRE listed here; see screenshot. To fix this problem, do the following: • Duplicate the existing entry (by hitting the Duplicate. Button) • Delete the original entry; it’s the one with checked checkbox in front of it.

• Then click Search. This should add two new entries to the list (see next screenshot). • Delete the entry you’ve created in step 1 (i.e.

The duplicate of the original entry). • Check one of the remaining entries. Note: The new two entries are linked. If you check one, both will be checked. Also, you can’t delete the entry for /System/Library/Java/.