Java is a strong, adaptable programming language invented by Sun Microsystems in 1995 (later bought by Oracle). It’s famed for its “Write Once, Run Anywhere” capabilities, meaning Java programs can operate on numerous operating systems without modification.
Key Features of Java
Object-Oriented → Java follows the concepts of OOP, making programming modular, reusable, and scalable.
Platform Independence → Java applications run on any OS with a JVM—no need for platform-specific customizations.
Security → Java offers sophisticated security features like bytecode verification and runtime security checks.
Multi-threading → Allows simultaneous execution of multiple tasks for higher performance.
The Java Development Kit (JDK) is an essential tool for developers building Java programs. It includes:
Java Compiler (javac) → Converts Java source code into bytecode that JVM can run.
Java Libraries → Provides pre-built methods and classes for quicker development.
JRE → Comes packed within the JDK to allow execution of built Java programs.
Debugger and Other Development Tools → Helps developers diagnose and optimize code.
When Do You Need JDK?
If you’re writing Java code, you must have the JDK.
If you merely wish to run Java apps, JDK isn’t required—JRE alone will serve.
The Java Runtime Environment (JRE) is designed for one major task—running Java applications. It contains:
JVM → The essential component that actually runs Java programs.
Java Libraries → Pre-written classes that Java programs can use.
Supporting Files → Helps ensure smooth operation of Java programs.
Why Do You Need JRE?
If you’re not a developer and merely need to execute Java apps.
If you want a lightweight version of Java without the development tools.
(Source: Java vs JRE vs Java JDK – What Smart Developer Must Know, Zypa)