Summary

Update the public no-args constructor of Swing's DebugGaphics class to document that it is not intended to be called by applications.

Problem

It is a mistake that the no-args constructor is public since it can't then be connected to a real Graphics instance to debug, and trying to use it just results in unexpected NPEs due to the uninitialised internal variable.

Solution

Update the javadoc of the DebugGraphics() constructor is updated to indicate that it is not intended to be called by applications and that it will result in a non-useful instance. The undocumented NPEs are resolved by creating a dummy Graphics which is what makes it non-useful, but no longer harmful.

Specification

  public class javax.swing.DebugGraphics 
    /**
     * Constructs a new debug graphics context that supports slowed
     * down drawing.
     * <p>
   +  * NOTE: This constructor should not be called by
   +  * applications, it is for internal use only. When called directly
   +  * it will create an un-usable instance.
     */
     public DebugGraphics() {