Use any of these options if you are having trouble running applets to confirm that you have a specific Java version.
The Java version can be found in the Java Control Panel.
The latest version(s) of Java on your system will be listed as Java 7 with an associated Update number (eg. Java 7 Update 21). Older versions may be listed as Java(TM), Java Runtime Environment, Java SE, J2SE or Java 2.
The Java Runtime (JRE) that you download from java.com or oracle.com contains a plugin to run Java content from your browser. In order to use the command line tools, you will need to download the Java Development Kit (JDK). The JRE and JDK are separate and can coexist on your system. Only one JRE can be installed on Mac OS X. There can be multiple JDKs installed on a system, as many as you wish.
Type the following in a Terminal window:
/Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java -version
When launching a Java application through the command line, the system uses the default JDK. It is possible for the version of the JRE to be different than the version of the JDK.
You can determine which version of the JDK is the default by typing
java -version in a Terminal window. If the installed version is 7u55, you will see a string that includes the text
java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)