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Comparison	JDK	JRE	JVM
Definition	A software development kit used to develop Java applications	A software package that contains what is required to run a Java application	An abstract computing machine that enables a computer to run a Java program
Includes	Compiler (javac), interpreter (java), libraries, documentation, other tools	Interpreter (java), libraries, Java Plug-in (for running Java applets in a web browser)	JIT, Libraries and class files
Purpose	To develop Java applications	To run Java applications	To execute Java bytecode
Installation	Required to develop Java applications	Required to run Java applications	Comes bundled with JDK or JRE

💡(1) J.V.M (Java Virtual Machine)-

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

💡-> J.v.m Doesn’t exists physically, It just resides in RAM

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

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

Note – We can’t refer any particular file as windows, it’s a group of specifications which provides environment to run software, similarly JVM only runs Java compiled codes(bytecodes).

*JVM internal architecture*-

💡(2)JRE (Java Runtime Environment)-

💡–> implementation of JVM.

💡–> physically exists.

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

Note – To run java program we only need to install JRE, to develop java program we need to install JDK.

💡(3)JDK (Java Development Kit)-

💡–> physically exists.

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

Interview Questions —

• How to install JVM?
• Is Windows JVM different than Linux/Mac JVM?
• Does installing JDK automatically installs JRE and JVM ?