The Java platform consists of three core components that work together to execute Java programs. Understanding the relationship between JDK, JRE, and JVM is fundamental to Java development.

JVM

Java Virtual Machine

An abstract computing machine that enables a computer to run Java programs and provides platform independence by executing bytecode.

Loads and verifies bytecode

Executes bytecode instructions

Manages memory and garbage collection

JRE

Java Runtime Environment

Implementation of JVM along with libraries and files needed to run Java applications.

Includes:

JVM (Java Virtual Machine)

Core libraries (java.lang, java.util, etc.)

Configuration files and resources

Note: Required to run Java programs, but cannot compile them.

JDK

Java Development Kit

Complete development kit for Java developers containing all tools needed to develop, compile, and run Java applications.

Development Tools:

JRE + JVM

Compiler (javac)

Debugger (jdb)

Documentation (javadoc)

Archive tool (jar)

Other utilities

How They Work Together

JDK ⊃ JRE ⊃ JVM

JDK contains JRE, which in turn contains JVM

To Run Java Programs

Install JRE (includes JVM and libraries)

To Develop Java Programs

Install JDK (includes JRE, JVM, and tools)

ThreadLocal

Code Examples

Use Cases

Common Mistakes to Avoid