6.2.4 The Runtime class

The Runtime class provides a series of methods for accesing the runtime environment of the Java VM. Some of these methods are detailed below. For a full list look at the Java API documentation.

exec	This method shells out and executes the specified command.
freeMemory	This method ryrns the amount of free memory left to the Java VM.
totalMemory	This method returns the total amount of memory assigned to the Java VM.

Source

Java API documentation.