JVM, JRE & JDK

 JVM

JVM (Java Virtual Machine) is an abstract machine. It is a specification that  provides runtime environment in which java byte code can be executed.

JVMs are available for many hardware and software platforms. JVM, JRE and JDK are  platform dependent because configuration of each OS differs. But, Java is platform independent.

The JVM performs following main tasks: Loads code Verifies code Executes code Provides runtime environment.                                        fig.Internal architecture of JVM    JRE JRE is an acronym for Java Runtime Environment. It is used to provide runtime environment. It is the implementation of JVM. It physically exists. It contains set of libraries + other files that JVM uses at runtime. Implementation of JVMs are also actively released by other companies besides Sun Micro Systems. JDK JDK is an acronym for Java Development Kit. It physically exists. It contains JRE + development tools.