Setting up the Sun Java Developer's Kit

Russell Bateman
Spring 2010
last update:

This is a very short treatise on quickly setting up the Sun Java Developer's Kit (JDK) for use with Eclipse.

If you originally installed a (whole) JDK (and not just a JRE) on your Windows box, you can just use that. I do not do this, but install the JDK separately (not under Program Files), though I have a JRE installed under Program Files for the benefit of the whole computer.

You must, however, download a JDK if you're doing real Java development as you'll need it for that. If you're doing C/C++, PHP, or something else, you might never need it and can just use a Java Runtime Environment (JRE). Eclipse already comes ready to use that and probably already works without you doing anything. If you're here in my pages, though, you're likely a Java developer since that's my only target audience.

The world of 64-bit

First, note that it is possible to get a 64-bit JRE(JDK) these days. I'm not going to discuss this in any detail except to point out that if you install a 64-bit Eclipse, you had better install a 64-bit JDK also. You cannot run Eclipse on a mismatched JDK. This is a common start-up problem among questions to the Eclipse newcomers' forum.

The Java developer's kit (JDK)

Download the JDK from http://java.sun.com/javase/downloads/widget/jdk6.jsp. These instructions were written when the current version was 1.6.0 20.

If you wish to install the JDK for the whole computer you're on, just download the JDK, install and then skip this document. (If you want things this way on Linux, prefer the .rpm download or its equivalent for Debian platforms.)

Installing the JDK privately

I advise installing a separate JDK for Eclipse's use because you're not at risk of it changing out from under you because of updates and you know exactly what version was used to develop your applications.

There are several methods of telling Eclipse where the JDK lives.

  1. Method 1: Place it in a subdirectory named jre under Eclipse's installation subdirectory.
  2. Method 2: Place a symbolic link to it in a subdirectory named jre under Eclipse's installation subdirectory.
  3. Method 3: Place it anywhere else and tell Eclipse where it is using eclipse.ini.

Method 1: Primary (local) JDK for Eclipse

This method is probably the least used, but it's very useful, it's the best solution unless you do not wish to violate the Eclipse distribution subdirectories. It involves simply downloading a JDK, unzipping (or untarring it) and placing it on the path eclipse/jre. You will have to create the jre subdirectory.

For the download, please read the instructions below, but don't put the JDK on a path like /home/russ/dev/downloads/jdk1.6.0_20. Instead, put it in the jre subdirectory you created under your Eclipse folder.

If you place the JDK local to Eclipse, you still need to edit eclipse.ini as discussed here because Eclipse will just find it there without help.

Method 2: Primary (semi-local) JDK for Eclipse

This method has the advantage of not copying the JDK. If you're installing Eclipse several times (for different purposes) and chose method 1, you'd be duplicating the JDK all over your host. This way, you just link to one copy.

Assuming the JDK on the path /home/russ/dev/jdk1.6.0_20, you can make the link easily enough: 

russ@tuonela:~/dev/eclipse/jre> ln -s ../../jdk1.6.0_20

This can also be done under Windows (since Vista only), but I haven't tried it for this purpose. "Symbolic links" under Windows seem to work well enough, but they're not very documented and I haven't used them very much. See Symbolic Links. Still assuming the JDK on C:\Users\russ\dev\jsdk1.6.0_20, ... 

C:\Users\russ\dev\eclipse\jre> mklink /d .\jdk1.6.0_20 ..\..\jdk1.6.0_20

You still need to specify the location of the JDK in eclipse.ini.

Method 3: Remote JDK for Eclipse

If you do not want to "violate" the Eclipse distribution by creating the jre subdirectory inside it, or you want the JDK somewhere in a more overt location, consider the method discussed here. You will have to edit eclipse.ini, in this case, to tell Eclipse where you have installed the JDK. Just download the JDK according the instructions below.

Return to Setting up Eclipse for the discussion on how to modify eclipse.ini.

Linux

When you go looking for a JDK, do not choose the download with "rpm" in the name. The other one (ending in .bin*) will unpack to a subdirectory, which is what you want. Place this directory on a path similar to /home/russ/dev/downloads/jdk1.6.0_20. Skip to after the (lengthy) Windows instructions below.

(* To unpack a .bin file on Linux, make it executable, then execute it.)

Windows

  1. Launch the JDK install executable that you downloaded.
    2.  
  2. Accept the end-user license agreement.
    3.  
  3. When it comes time to deviate from the ordinary set-up, change the place to install to. Normally, it wants to be installed here:

    4.  
  4. Instead, click Change and navigate or type in the path to where you want to keep it. My favorite place is a downloads subdirectory under my development directory. You will have to retype the correct installation directory name since you decided to change where to install it. You may have forgotten that it was (in this case and at the time I did this) jdk1.6.0_20.

    5.  
  5. Ultimately, we're back on track with the new place and we click Next.

    6.  
  6. Later on, you might very well encounter a separate installation wiggle that wants to install the JRE separately on the usual, for-the-whole-computer path.

    I resist this too since I want to administer my computer's Java runtime environment separately from development issues (though this certainly doesn't hurt anything as you won't need to use the JRE installed under your JDK).

    7.  
  7. So, here's where I decide to put the JRE—that my computer won't be using—just to be totally orthogonal.

  8. Click OK, then finish the installation as you normally would.

    Note: Installation launches your browser on a page that wants registration. This is not necessary and you can just close the page.

Both Linux and Windows

If you've accomplished this installation correctly, you're now ready to install Tomcat, if you want this as your web container server, or you can go on to install Eclipse at this point.

If you install Tomcat, do the same thing as was shown here instead of installing it for your whole computer (or, in addition to doing that). See Setting up Apache Tomcat.