Step 3:Java Components (jvm,jre,jdk) : 1st hour

(a) J.V.M (Java Virtual Machine)-

J.v.m = j.i.t(just-in-time compiler)+cache

-J.v.m Doesn’t exists physically,

-J.v.m provides specifications to execute java byte-code.

-J.v.m is platform dependent and easily available for many platforms(OS)


*JVM internal architecture*-


(b)JRE (Java Runtime Environment)-

– implementation of JVM.

– physically exists.

JRE = JVM + Set of libraries (i.e. jar) + Other Files


(c)JDK (Java Development Kit)-

– physically exists.

JDK = JRE + Development tools(i.e. javac, java etc)



  1. you can consider jvm as a computer for which machinre language is bytecode .
    And jre builds this virtiual computer (i.e jvm) on your machine(p.c) so it can run program .

  2. yes, of course…
    Basic Tools
    These tools are the foundation of the JDK. They are the tools you use to create and build applications.
    1-javac The compiler for the Java programming language.
    2-java The launcher for Java applications.
    3-javadoc API documentation generator.
    4-apt Annotation processing tool.
    5-jar Create and manage Java Archive (JAR) files.
    6-jdb The Java Debugger.
    7-javap Class file disassembler

  3. Sir can you plz elaborate some useful tools(Java,javaw,javap etc.) of jdk

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