1. Difference between JVM/JRE/JDK ?                            

                                java virtual machine(JVM)

JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode 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                                                        Java Runtime Environment(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.                                 Java Development Kit(JDK) JDK is an acronym for Java Development Kit.It physically exists.It contains JRE + development tools.