Java on Mac OSX

Notes to myself about Java on Mac OS X since I always forget and have to Google it every time.

• How do you find all the Java installed on your Mac?
  /usr/libexec/java_home -V


• How do you set JAVA_HOME to a specific version?
  export JAVA_HOME=`/usr/libexec/java_home -v 1.6`


• How do you execute a specific version of Java to run?
  /usr/libexec/java_home -v 1.6 --exec javac -version


• What is the difference between the Java in /System/Library and /Library?
  The Java in /System/Library is the version of Java from Apple. Apple uses it for its system runtime so do not touch or modify it.  The Java in /Library is what you installed from Sun.
  


• Where do you put Java Extensions?
  In directory /Library/Java/Extensions