During execution, how can a java program tell how much memory it is using?

During execution, how can a java program tell how much memory it is using?

I don’t care how efficient it is!

Answer

VonC’s answer is an interactive solution – if you want to know programatically, you can use Runtime.totalMemory() to find out the total amount used by the JVM, and Runtime.freeMemory() to find out how much of that is still available (i.e. it’s allocated to the JVM, but not allocated within the JVM – new objects can use this memory).

These are instance methods – use Runtime.getRuntime() to first get the singleton instance.