Question

I compile with javac helloswing.java but cannot run with java swingtutorial.helloswing as it said Exception in thread main NoClassDefFoundError. Could not find main class

I just added classpath to c:…\rt.jar but still java -cp . swingtutorial.helloswing cannot find main why ?

package swingtutorial;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class helloswing extends JFrame {

    public helloswing() {
       setTitle("Hello Swing");
       setSize(300, 200);
       setLocationRelativeTo(null);
       setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                helloswing ex = new helloswing();
                ex.setVisible(true);
            }
        });
    }
}

Answer 1

You need to specify the classpath. Try with

javac swingtutorial\helloswing.java
java -cp . swingtutorial.helloswing