Java 6 and Java 7 on Windows

I am an Android Developer, and recently I started playing around with <a href="http://vertx.io/">vert.x</a>, if you haven't already, check it out. so I ran into some problems shortly after adding the necessary jar files to my project ... turns out vert.x requires Java 7. This was not to big of a problem for me on Mac OS X. Just run the Java 7 installer and ( to my surprise ) Eclipse found the new JDK. Java 6 was still my default Java installation which I was fine with.

Shortly, after I decided to give vert.x a shot on Windows 8 ( Samsung Series 7 Laptop, My new toy! :) ). So, first thing i did was run the installer I downloaded from <a href="http://www.oracle.com/technetwork/java/javase/downloads/java-se-jdk-7-download-432154.html">here</a>. Of course the installer runs fine and my default Java installation becomes Java 7.
So, here is the reason I am writing this pro tip. I wanted a simple way to switch between Java 7 and Java 6 on my machine without to much of a headache.

From this point forward I am assuming you have installed both <a href="http://www.oracle.com/technetwork/java/javase/downloads/jdk6-downloads-1637591.html">Java 6</a> and <a href="http://www.oracle.com/technetwork/java/javase/downloads/java-se-jdk-7-download-432154.html">Java 7</a> on your machine. For me both installers run perfect.

If you have some experience with java you know that JAVA_HOME is a common environment variable to set so that Java can be located on your machine. So, first we will go ahead and set that environment variable. Search for "Environment Variables" -> Settings -> Edit the System Environment Variables, which should popup a dialog something like this :

Inside this dialog you will want to add 3 Environment Variables to the System.

1. JAVA6_HOME = { Location of Java 6 Installation }
2. JAVA7_HOME = { Location of Java 7 Installation }
3. JAVAHOME = %JAVA7HOME% - this variable will change, when you want to a different JDK.

It should look something like this :

After you have resolved the different JDK's on the system, you need to add %JAVAHOME%\bin to your PATH Environment Variable.
**NOTE : The windows installer's for Java put java.exe in your System32 folder so that you can run Java without setting environment variables. When adding %JAVAHOME%\bin to your PATH make sure that it appears before C:\Windows\System32, or you can delete the java.exe from C:\Windows\System32*

Path or PATH should now contain %JAVA_HOME%\bin :

Now, lets test it out.

Open a Command Prompt and type "java -version". You should a version number starting with "1.7.0_" .

Now lets go back to Java 6. Easy, just go back and change JAVAHOME from %JAVA7HOME% to %JAVA6_HOME% :
NOTE : Be sure to close your command prompt, because Environment Variables will not refresh without a restart of the Command Prompt

Open a Command Prompt and type "java -version". You should see a version number starting with "1.6.0_".
.

I realize it's not perfect, but it is easy enough for me. It is much easier than uninstalling / reinstalling the JDK's to make sure the right one is installed in C:\Windows\System32\