Answer Posted / alok kumar ranjan

JRE :- (Java Runtime environment)
It is an implementation of the Java Virtual Machine* which
actually executes Java programs.Java Run Time Environment is
a plug-in needed for running java programs.JRE is smaller
than JDK so it needs less Disk space.JRE can be
downloaded/supported freely from java.com
It includes JVM , Core libraries and other additional
components to run applications and applets written in Java.

JDK :- (Java Development Toolkit)
It is a bundle of software that you can use to develop Java
based applications.Java Development Kit is needed for
developing java applications.JDK needs more Disk space as it
contains JRE along with various development tools.JDK can be
downloaded/supported freely from java.sun.com
It includes JRE, set of API classes, Java compiler, Webstart
and additional files needed to write Java applets and
applications.


JVM : Java Virtual Machine converts the bytecode into user
understandable code. without JVM we cannot run our Java
codes on any system. JVM converts the bytecode got after
compilation into machine level code by understanding the
hardware and operating system combination.

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