What Is Java?

Java is a general-purpose, object-oriented programming language. Source code is compiled into an intermediate form called bytecode, which runs on the Java Virtual Machine (JVM) rather than directly on a specific processor.

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, world!");
    }
}

That JVM layer is the source of Java's famous "write once, run anywhere" promise — the same compiled .class file runs unchanged on Windows, macOS, or Linux, as long as each has a JVM installed. Java is statically typed (every variable's type is fixed and checked at compile time) and strictly object-oriented — even a simple program's entry point must live inside a class.