Add the line: export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64 (use your actual path) Refresh: source ~/.bashrc 6. Performance Tuning for Linux
| Issue | Solution | |-------|----------| | java: command not found | JRE not installed or not in PATH. Reinstall or fix $PATH . | | Error: Could not find or load main class | Wrong class name (case-sensitive) or missing classpath. Use java -cp . ClassName . | | Unsupported major.minor version | JRE older than compiled class version. Install newer JRE. | | JAVA_HOME should point to a JDK not a JRE | For build tools (Maven, Gradle). Either install JDK or set JAVA_HOME to JDK path. | | java.net.ConnectException: Connection refused | Network/firewall issue, not JRE fault. Check iptables / firewalld . | jre linux
: The JRE's core strength is the "Write Once, Run Anywhere" (WORA) promise. Programs compiled on Windows or macOS generally run flawlessly on Linux without modification. | | Error: Could not find or load
// Hello.java public class Hello public static void main(String[] args) System.out.println("JRE works! Version: " + System.getProperty("java.version")); | | Unsupported major
Even if you only need the JRE, many applications check JAVA_HOME . Point it to the JRE installation directory.
sudo dnf install java-11-openjdk-headless