Java Virtual Machine

Introduction

The Java Virtual Machine is the most important component of the Java platform. The JVM is an abstract computing machine. The first prototype implementation of the JVM was done at Sun Microsystems, Inc.

The JVM knows only the binary class file format. A class file contains JVM instructions (or bytecodes), a symbol table, and other information. JVM provides the runtime environment in which java bytecode can be executed. The bytecode is generated by a Java compiler in a JVM understandable format. JVM has an Instruction Set and manipulates memory at run time.

JVM is responsible for Java code hardware & operating system independence. The JVM does not assume any particular implementation technology, host hardware, or host operating system.

JVM Types

JVM has a specification. JVMs are available for many hardware and software platforms(JVM is platform-dependent).

  • Java HotSpot Client VM
  • Java HotSpot Server VM

The Java HotSpot Client VM is the default virtual machine of the Java SDK and JRE. It is tuned for best performance when running applications in a client environment by reducing application start-up time and memory footprint.

The Java Hotspot Server VM loads more slowly, putting more effort into producing highly optimized JIT compilations that yield higher performance. HotSpot Server VM is designed for maximum program execution speed.

JVM Specification

JVM specification is a specification or blueprint for the virtual machine. The implementation details are not part of the JVM specification. The JVM should be able to read the Java class file format and perform the operations specified correctly.

JVM Examples

Some of the JVM Examples are:

  • HotSpot JVM
  • Eclipse OpenJ9 JVM

HotSpot

The HotSpot is a JVM for desktop and server computers, developed by Sun Microsystems. HotSpot JVM is now maintained and distributed by the Oracle Corporation.

Eclipse OpenJ9

Eclipse OpenJ9 is a fast, efficient, high-performance, and enterprise-class JVM that delivers power and performance.

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Java Tutorials

Java Tutorial on this website:

https://www.testingdocs.com/java-tutorial/

For more information on Java, visit the official website :

https://www.oracle.com/java/

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