Installing Java (JDK, JRE, JVM)

Before you can develop and run Java applications, you need to install the appropriate Java environment.

JVM – Java Virtual Machine

The JVM is the engine that executes Java bytecode. It is platform‑specific and provides the runtime environment.

JRE – Java Runtime Environment

The JRE includes the JVM plus core libraries and other components needed to run existing Java programs. It does not include development tools like the compiler.

JDK – Java Development Kit

The JDK contains the JRE plus development tools such as:

javac – the Java compiler (source → bytecode)
jar – archiver
javadoc – documentation generator
jdb – debugger

How to install

Choose a JDK distribution – Oracle JDK, OpenJDK, Adoptium, Amazon Corretto, etc.
Download the installer for your operating system from the official site (e.g., adoptium.net).
Run the installer and follow the instructions.
Set environment variables (optional, but recommended):
- JAVA_HOME – path to the JDK installation directory.
- Add %JAVA_HOME%\bin (Windows) or $JAVA_HOME/bin (macOS/Linux) to your PATH.

Verify installation

Open a terminal/command prompt and run:

java -version
javac -version

You should see version information confirming that both java (the launcher) and javac (the compiler) are available.