Installing the JDK and choosing an editor

Understanding Installing the JDK and choosing an editor

Java is developed as source in the OpenJDK project, and what you download is one vendor's compiled build of that source: Eclipse Temurin, Amazon Corretto, Azul Zulu, Microsoft's build, Oracle's build. For learning they are interchangeable, because the compiler and the language are the same; the differences are how long each vendor keeps patching a release and under what licence. What does matter is the feature release number, since a JDK can always compile and run code written for older releases but never read class files produced by a newer one. Pick a long-term-support release such as 17, 21 or 25 and you will not have to re-download every six months.

Installing a JDK unpacks a directory tree whose bin folder holds java, javac, jar and the other tools; nothing about it registers itself with the language. Your shell locates those programs through PATH, so when several JDKs are present the one that answers java is whichever bin directory comes first, not the one you installed most recently. JAVA_HOME is a separate convention that Maven, Gradle and many scripts read to find a JDK, and it points at the install root, the parent of bin. Because PATH and JAVA_HOME can disagree, treat java -version and the java.home system property as the only reliable answer to which JDK is active.

Choosing an editor is an independent decision, because no editor compiles Java; the JDK does. A plain text editor plus a terminal is entirely sufficient and keeps the toolchain visible, while IntelliJ IDEA Community Edition, VS Code with the Java extensions, Eclipse and NetBeans add navigation, refactoring and live error checking by running their own analysis against a JDK you select per project. That project setting is the part beginners overlook: the IDE's configured JDK and release level, not your PATH, decide what the IDE accepts, which is why one file can compile cleanly in a terminal and still show errors in the editor.

public class ShowJdk {
    public static void main(String[] args) {
        System.out.println("java.version = " + System.getProperty("java.version"));
        System.out.println("java.vendor  = " + System.getProperty("java.vendor"));
        System.out.println("java.home    = " + System.getProperty("java.home"));
        System.out.println("feature      = " + Runtime.version().feature());
    }
}

Worked examples

import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;

public class CompilerCheck {
    public static void main(String[] args) {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        if (compiler == null) {
            System.out.println("No compiler here: this is a runtime, not a JDK.");
        } else {
            System.out.println("Compiler found: " + compiler.getClass().getSimpleName());
            System.out.println("Full JDK, javac is available.");
        }
    }
}

public class Probe {
    record Point(int x, int y) {}

    public static void main(String[] args) {
        var p = new Point(2, 3);
        System.out.println(p);
        System.out.println("Compiled, so this JDK is 16 or newer.");
    }
}

import java.nio.file.Path;

public class WhereIsJavac {
    public static void main(String[] args) {
        Path home = Path.of(System.getProperty("java.home"));
        System.out.println("JAVA_HOME should be: " + home);
        System.out.println("PATH needs: " + home.resolve("bin"));
    }
}

Important notes

Common mistakes

Try it yourself