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

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DefinitionA software development kit used to develop Java applicationsA software package that contains what is required to run a Java applicationAn abstract computing machine that enables a computer to run a Java program
IncludesCompiler (javac), interpreter (java), libraries, documentation, other toolsInterpreter (java), libraries, Java Plug-in (for running Java applets in a web browser)JIT, Libraries and class files
PurposeTo develop Java applicationsTo run Java applicationsTo execute Java bytecode
InstallationRequired to develop Java applicationsRequired to run Java applicationsComes 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 ?


    • 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

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