FULL PRODUCT VERSION :
java version "1.5.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta-b32c)
Java HotSpot(TM) Client VM (build 1.5.0-beta-b32c, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
 customer  Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
When I call the method getSuperClass on the StringBuilder i get a class AbstractStringBuilder instead of  customer . I also noticed that the AbstractStringBuilder  contains methods with a corresponding  signature, (see code below). Is the signature of the method changed or does the keyword volatile hide the method.

package java.lang;

import java.io.IOException;
import sun.misc.FloatingDecimal;

abstract class AbstractStringBuilder
    implements Appendable, CharSequence
{

	....


    public AbstractStringBuilder append(CharSequence charsequence)
    {
    }

	....

    public AbstractStringBuilder append(char c)
    {
    }

	....

    public volatile Appendable append(char c)
        throws IOException
    {
    }

    public volatile Appendable append(CharSequence charsequence)
        throws IOException
    {
    }
}


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
StringBuilder.class.getSuperclass()

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I would expect the super class of the StringBuilder would be Object as indicated in the documentation
ACTUAL -
Super class StringBuilder: class java.lang.AbstractStringBuilder

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
/*
 * TestStringBuilder.java
 *
 * Created on March 30, 2004, 2:34 PM
 */

import java.lang.StringBuilder;

/**
 *
 * @author  schenk_m
 */
public class TestStringBuilder {
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        System.out.println("Super class StringBuilder: " +
                StringBuilder.class.getSuperclass());
    }
    
}
---------- END SOURCE ----------
(Incident Review ID: 245603) 
======================================================================
  xxxxx@xxxxx   10/20/04 22:46 GMT

N/A

getSuperclass returns the real superclass of StringBuilder, the documentation reports public classes only.
  xxxxx@xxxxx   2004-04-08

Current behavior is as expected.
Information on the documentation-related aspects of this can be
found in the bug reports noted in the "See Also" section.
  xxxxx@xxxxx   10/20/04 22:46 GMT

Take a look at bug: 4874845 (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4874845) 

It seems to be the decision, that non-public classes should be hidden from the API-user's eye. But the way of declaring that Object is the superclass really is a lie. 
I found an additional bug related to the StringBuffer/Builder redesign in 1.5.0 that will require to declare AbstractStringBuilder public, if not dropped. That solution will make this one obsolete, but it should be discussed, what policy javadoc should follow...