The Java Virtual Machine serves as the main interpreter for Java bytecodes, and consists of a bytecode instruction set, a set of registers, a stack, a heap, and a method storage area.
Visibility
The level of access that methods and instance variables expose to other classes and packages. You define visibility using the modifiers public , protected , and private (note that there is also default visibility, though you don't write default explicitly).
void
Java keyword used to indicate in a method declaration that the method does not return any value. Methods returning void return implicitly when they complete the final statement. Note that this does not mean that use of the return keyword is mutually exclusive with use of the void return type ”that is, the following is perfectly legal (but probably useless): public void dumbMethod(){ return; } .
volatile
A modifier indicating that a variable can be accessed and modified asynchronously by concurrent threads. For example: volatile int myNumber; .