JDK-vs-JRE-vs-JVM
Keypoints
- JDK (Java Development Kit): A complete set of tools for developing Java applications; Includes compiler, libraries, and JRE.
- JRE (Java Runtime Environment): runtime environment for Java applications; Includes JVM and core libraries.
- JVM (Java Virtual Machine): executes Java bytecode; It frees up stage and manages memory.
Definition
The Java Development Kit (JDK), Java Runtime Environment (JRE), and Java Virtual Machine (JVM) are essential components of the Java ecosystem.
- The JDK is a comprehensive toolkit used for developing Java applications, encompassing the compiler, debuggers, other development tools, and the JRE.
- The JRE is designed to run Java applications and includes the JVM, standard libraries, and other runtime components necessary for executing Java programs.
- At the core, the JVM is a virtual machine that interprets and executes Java bytecode, providing platform independence by allowing the same Java program to run on any device with a compatible JVM. Together, these components enable the development, compilation, and execution of Java applications.
JDK (Java Development Kit)
Definition: The JDK is a software development kit used to develop Java applications. It provides the tools necessary for Java development, including the compiler (javac), the Java Runtime Environment (JRE), and other tools like debuggers and documentation generators.
Components:
- Compiler: Converts Java source code (.java files) into bytecode (.class files).
- JRE: Included within the JDK to run Java programs.
- Development Tools: Includes tools such as javadoc for documentation and javap for class file disassembly.
- Usage: Used by developers to write, compile, debug, and execute Java applications.
JRE (Java Runtime Environment)
Definition: The JRE provides the libraries, Java Virtual Machine (JVM), and other components necessary to run Java applications. It does not include development tools like compilers or debuggers.
Components:
- JVM: Executes the bytecode.
- Class Libraries: Standard Java libraries are required for running Java programs.
- Other Components: Includes components necessary for Java applet execution and graphical user interface (GUI) applications.
- Usage: Used by end-users to run Java applications on their devices. It is part of the JDK but can be downloaded separately for running Java applications.
JVM (Java Virtual Machine)
Definition: The JVM is a virtual machine that enables a computer to run Java programs. It interprets the compiled Java bytecode and executes it on the host machine, providing platform independence.
Components:
- Class Loader: Loads class files into the JVM.
- Bytecode Verifier: Ensures the bytecode adheres to Java language specifications and does not violate any access restrictions.
- Interpreter/Just-In-Time Compiler (JIT): Executes the bytecode. The JIT compiler improves performance by compiling bytecode into native machine code at runtime.
- Usage: Provides the runtime environment to execute Java bytecode. It is part of both the JDK and JRE.
