ADDITIONAL SYSTEM INFORMATION :
Observed on Windows and Mac OSX. Should occur on other platforms too.

A DESCRIPTION OF THE PROBLEM :
The plugin access to Unsafe and got java.lang.NoClassDefFoundError: sun/misc/Unsafe
When run with jdk 11 outside jconsole launcher, the class is resolved.
Even java -cp TestJConsoleJDK11.jar sun.tools.jconsole.JConsole works fine.

REGRESSION : Last worked in version 10.0.2

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Simplest plugin to access to unsafe in getTabs.


---------- BEGIN SOURCE ----------
import com.sun.tools.jconsole.JConsolePlugin;
import java.awt.BorderLayout;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
import sun.misc.Unsafe;

/**
 *
 * @author jdenise@redhat.com
 */
public class TestJConsoleJDK11 extends JConsolePlugin {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {
        // TODO code application logic here
        System.out.println(getUnsafe().addressSize());
    }

    @Override
    public Map<String, JPanel> getTabs() {
        int size = -1;
        try {
            size = getUnsafe().addressSize();
        } catch (IllegalArgumentException | IllegalAccessException | NoSuchFieldException ex) {
            Logger.getLogger(TestJConsoleJDK11.class.getName()).log(Level.SEVERE, null, ex);
        }
        Map<String, JPanel> panelMap = new HashMap<String, JPanel>();
        JPanel jconsolePanel = new JPanel(new BorderLayout());
        panelMap.put("Test" + size, jconsolePanel);
        return panelMap;
    }

    @Override
    public SwingWorker<?, ?> newSwingWorker() {
        return null;
    }

    private static Unsafe getUnsafe() throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException {
        Field f = Unsafe.class.getDeclaredField("theUnsafe");
        f.setAccessible(true);
        Unsafe unsafe = (Unsafe) f.get(null);
        return unsafe;
    }

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Add --add-modules=jdk.unsupported when launching jconsole.

FREQUENCY : always