Setting up Java

Java is a statically typed, object-oriented language that runs on the Java Virtual Machine (JVM). It powers banking systems, Android apps, large web back-ends and big-data tools. Install a JDK (Java Development Kit) — version 21 LTS or newer — from adoptium.net, then check with java -version.

Every Java program starts in a main method inside a class. The file name must match the public class name: class Hello lives in Hello.java.

Since Java 11 you can run a single source file directly with java Hello.java — ideal for learning. Larger projects compile with javac (or a build tool such as Maven) into .class files that the JVM runs. IntelliJ IDEA Community and VS Code with the Java extensions are excellent free editors.

import java.time.Year;

public class Hello {
    public static void main(String[] args) {
        String name = "Dolese";
        int year = Year.now().getValue();
        System.out.println("Hello, " + name + "! Welcome to Java in " + year + ".");
    }
}

java -version
java Hello.java            # compile and run in one step

javac Hello.java           # or: compile to Hello.class ...
java Hello                 # ... then run the compiled class

public class About {
    public static void main(String[] args) {
        String name = args.length > 0 ? args[0] : "Amina";
        System.out.println("Name: " + name);
        System.out.println("School: Azania Secondary");
        System.out.println("Favourite subject: Biology");
    }
}

java About.java Juma
# Name: Juma
# School: Azania Secondary
# Favourite subject: Biology