- Java Programming Basics
- Java Tutorial
- Java Environment Setup
- Java Separators
- Java Data Types
- Java Variables
- Java Variable Scope
- Java Type Casting
- Java Operators
- Java Increment Decrement
- Java Left Shift
- Java Right Shift
- Java Bitwise Operators
- Java Ternary Operator
- Java Control Statements
- Java if-else statement
- Java for Loop
- Java while Loop
- Java do-while Loop
- Java switch Statement
- Java break Statement
- Java continue Statement
- Java Popular Topics
- Java Arrays
- Java Multidimensional Array
- Java Strings
- Java Methods
- Java Date and Time
- Java Exception Handling
- Java File Handling
- Java OOP
- Java Classes and Objects
- Java Constructors
- Java Constructor Overloading
- Java Object as Parameter
- Java Returning Objects
- Java Encapsulation
- Java Abstraction
- Java Inheritance
- Java Polymorphism
- Java Packages
- Java Import Statement
- Java Multithreading
- Java Suspend Resume Stop Thread
- Java Programming Examples
- Java Programming Examples
Difference Between JVM, JRE, and JDK in Java (Explained Simply)
JRE and JVM are the components of the JDK (Java Development Kit), which is a comprehensive software package used to create, compile, and run Java applications.
Java is a widely used programming language used to create a vast array of applications across various platforms, such as Android apps, enterprise software, web applications, big data technologies, Internet of Things (IoT), cloud-based applications, game development, scientific applications, and desktop GUI applications.
Java is a popular choice among developers because of its core features like platform independence, object-oriented programming, security, a large community, and a rich ecosystem. In this article, we will learn about JVM, JRE, and JDK as they form the core ecosystem for building and running applications.
Requirements of JVM, JRE, and JDK
JVM, JRE, and JDK are three different hierarchical concepts in Java that are closely related to each other, but each is distinct and defines its own roles and responsibilities.
JVM stands for Java Virtual Machine, which is the core engine that executes bytecode; the JRE (Java Runtime Environment) contains the JVM and provides the environment to run compiled Java applications; the JDK (Java Development Kit) is a complete toolkit for Java developers, including the JRE and development tools. JDK is used to develop, compile, debug, and monitor Java applications.
- Requirement of JVM: To interpret and execute Java bytecode into machine-specific code. The feature of "write once, run anywhere" is provided through this engine.
- Requirement of JRE: Provides a runtime environment to run Java programs. It also contains the JVM, core class libraries, and supporting files.
- Requirement of JDK: A complete kit for developing Java applications containing the JRE and development tools.
Brief Description of JVM (Java Virtual Machine)
The JVM (Java Virtual Machine) is a virtual machine that executes a Java program by running the bytecode generated by the compiler.
How JVM Works
First, the program is written by the programmer in Java. Then, it is converted into bytecode by the compiler, which translates the high-level program before running. The machine code, also known as bytecode, consisting of a sequence of 0s and 1s, is read by the JVM. The JVM converts the bytecode into native machine code which runs on the system.
Role of JVM
- Loads Java bytecode
- Verifies code for security
- Converts bytecode into machine code
- Executes the program
- Manages memory automatically
Key Components of JVM
- Class Loader: It dynamically loads Java classes into memory during program execution. It is responsible for locating, loading, and linking the .class files needed by a Java application only when they are required.
- Bytecode Verifier: The primary role of this component is to protect the integrity of the JVM and prevent incorrectly generated code through a multi-layered security model. It acts as a gatekeeper.
- Runtime Data Areas: It is the memory area within the Java Virtual Machine (JVM) where all data is stored during the execution of a program. It includes heap memory, stack memory, and method area.
- Execution Engine: It is responsible for executing Java programs by translating bytecode into native machine code.
Brief Description of JRE (Java Runtime Environment)
The JRE provides everything needed to run Java applications on any machine. It includes the JVM (Java Virtual Machine), core libraries, and supporting files required for running Java programs. It does not include development tools like compilers or debuggers.
Components of JRE
Given below is the list of components of JRE.
- Integration libraries include Java Database Connectivity (JDBC)
- Java Naming and Directory Interface (JNDI)
- Interface Definition Language (IDL)
- Remote Method Invocation Over Internet Inter-Orb Protocol (RMI-IIOP)
- Remote Method Invocation (RMI)
- Scripting
Importance of JRE
Java Runtime Environment provides the platform for executing Java programs and enabling Java’s core principle of “Write Once, Run Anywhere”. Given below is the list describing the importance of JRE.
- Platform Independence: JRE allows Java programs to run on any operating system such as Windows, macOS, Linux, etc.
- Execution Environment: The JRE manages the execution of Java code, providing all necessary resources like memory allocation, system libraries, and security features.
- Memory Management: The JRE comes with built-in memory allocation such as heap, stack, and method area.
- Security: The JRE comes with built-in security features that isolate Java applications from the host system to prevent theft and malicious activity.
- Rich Source of Libraries and APIs: The JRE comes with built-in libraries and APIs that provide user interface toolkits, networking and database connectivity, and utility packages.
Brief Description of JDK (Java Development Kit)
The JDK stands for Java Development Kit, which is a software development kit that provides tools and libraries needed to build Java-based applications and applets. It works together with the JVM (Java Virtual Machine) and JRE (Java Runtime Environment) as part of the core Java setup.
The JDK includes everything required for building applications such as compilers, debuggers, and other essential tools. Given below is the list of software tools that JDK contains.
- Java Runtime Environment (JRE)
- An interpreter/loader (Java)
- A compiler (javac)
- An archiver (jar)
Importance of JDK
- Development Environment: The JDK contains fundamental tools like a compiler, debugger, packaging tool, and documentation generator to transform Java code into runnable applications.
- Platform Independence: With the use of Java Virtual Machine (JVM) and Java Runtime Environment (JRE), the JDK allows compiled bytecode to run on any operating system.
- Enables Advanced Features: Provides access to APIs and utilities for Object-Oriented Programming, multithreading, and enterprise features that facilitate dynamic and scalable applications.
Conclusion
JVM, JRE, and JDK are the backbone of building Java applications. In short, JVM executes Java programs, JRE provides the environment to run the code, and JDK offers tools to develop the applications. Working together, they enable Java platform independence, security, and reliability.
« Previous Tutorial Next Tutorial »