Setting the JAVA_HOME environment variable differs on different platforms.

Windows

• Open System Properties (right-click "My computer" and select "Properties")
• Open "Advanced" tab
• Click "Environment Variables"
• Locate the "JAVA_HOME" system variable en click "Edit"
• Set the value of the variable to the path of the Java installation, for example: "C:\Progra~1\Java\jre1.6.0_17"

Macintosh

setenv JAVA_HOME /System/Library/Frameworks/JavaVM.framework/Home

Unix

Depending on the used shell

export JAVA_HOME="/usr"

declare -x JAVA_HOME="/usr"