JDK, JRE & JVM

Java development kit 


The Java Development Kit (JDK) is a software development environment used for developing Java applications and applets. It includes the Java Runtime Environment (JRE), an interpreter/loader (java), a compiler (javac), an archiver (jar), a documentation generator (javadoc) and other tools needed in Java development.

 Java runtime environment 

JRE is an acronym for Java Runtime Environment.It is used to provide runtime environment.It is the implementation of JVM. It physically exists. It contains set of libraries + other files that JVM uses at runtime.

Implementation of JVMs are also actively released by other companies besides Sun Micro Systems.

 Java virtual machine 

A Java virtual machine (VM) is software that implements the Java runtime system and executes Java applications. It can be a standalone application like the java command that comes with the JDK or built into a larger application like a web browser. Usually the interpreter itself is a native application, supplied for each platform, which then bootstraps other tools written in the Java language. Tools such as Java compilers and IDEs are often implemented directly in Java to maximize their portability and extensibility. NetBeans, for example, is a pure-Java application.

The Java VM performs all the runtime activities of Java. It loads Java class files, verifies classes from untrusted sources, and executes the compiled bytecode. It manages memory and system resources. Good implementations also perform dynamic optimization, compiling Java bytecode into native machine instructions.


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