This bug was originally detected by the failing test case
test/java/awt/dnd/DnDAcceptanceTest. We have created a new test case which does
not involve DnD.

import java.applet.Applet;
import java.awt.Button;
import java.awt.event.MouseAdapter;
import java.io.*;

public class DnDAcceptanceTest extends Applet {
    public static void main(String[] args) {
        final Button src = new Button();
        src.addMouseListener(new Adapter());
        testSer(src);
    }

    public void init() {
        final Button src = new Button();
        src.addMouseListener(new Adapter());
        testSer(src);
    }

    public static void testSer(Object o) {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(o);
            ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
            ObjectInputStream ois = new ObjectInputStream(bais);
            Object copy = ois.readObject();
            System.err.println("copy=" + copy);
        } catch (Throwable ex) {
            ex.printStackTrace();
        }
    }
}

class Adapter extends MouseAdapter implements Serializable {}



This test passes when run as a standalone application.
However if you run this test in appletviewer deserialization will fail
with exception:

java.lang.ClassNotFoundException: Adapter
        at java.lang.ClassLoader.findClass(ClassLoader.java:355)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:303)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:259)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:195)
        at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:489)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1365)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1288)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1489)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1161)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:283)
        at java.awt.Component.readObject(Component.java:6528)
        at sun.misc.Unsafe.invokeSpecial(Native Method)
        at sun.misc.ClassReflector.invokeSpecial(ClassReflector.java:376)
        at $ClassReflector1.readObject(Unknown Source)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1585)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1508)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1161)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:283)
        at DnDAcceptanceTest.testSer(DnDAcceptanceTest.java:26)
        at DnDAcceptanceTest.init(DnDAcceptanceTest.java:16)
        at sun.applet.AppletPanel.run(AppletPanel.java:344)
        at java.lang.Thread.run(Thread.java:579)

This failure is reproducible on builds b46-b50 and not reproducible on
b40. I'm not sure whether this is a ClassLoader bug or a Serialization bug.
Filing bug based on stack trace for now.