What is JVM, JDK, and JRE?Explained in Simple Words (Notes)

Java has a powerful architecture that makes it platform-independent, secure, and robust. But to truly understand how Java works, you need to know the difference between:

• 🔥 JVM (Java Virtual Machine)
• 📦 JRE (Java Runtime Environment)
• 🛠️ JDK (Java Development Kit)

1️⃣ JVM (Java Virtual Machine)

🧠 JVM is the brain behind Java.

What it does:

• It runs Java bytecode (compiled .class files).
• Converts bytecode into machine-specific instructions.
• Provides features like: Garbage collection, Memory management, Security and runtime optimization.

Analogy:

Think of JVM as a translator who reads your bytecode and speaks to your operating system in its own language (machine code).

Important:

Every OS (Windows, macOS, Linux) has its own version of JVM.

2️⃣ JRE (Java Runtime Environment)

⚙️ JRE is a software package that contains everything needed to run a Java program.

What it includes:

• JVM (Java Virtual Machine)
• Libraries and class files needed at runtime (like rt.jar)
• Other supporting files