Bug 86135 Make use of new IResource#revertModificationStamp(long) API
org.eclipse.ltk.core.refactoring/src/org/eclipse/ltk/core/refactoring/ContentStamp.java
* performing a corresponding undo change.
 * <p>
 * Clients of the refactoring framework don't need to take care of content
 * stamps. They are managed by the framework itself.
 * </p>
 * <p>
 * Not all files in the workspace are annotated with a content stamp. The 
 * refactoring framework only adds content stamp to those files where necessary.
 * </p>
 * <p>
 * Content stamp are to be compared using the <code>equals(Object)</code> method.
 * It is not guaranteed that content stamp are identical for identical files.
 * </p>
 * <p>
 * This class is not intended to be extended by clients.
 * </p>
 * 
 * @since 3.0
 */
public abstract class ContentStamp {
	/**
	 * Checks whether the stamp is the null stamp or not. A null stamp
	 * is generated for files which either don't exist or exist in a 
	 * closed project.
	 * 
	 * @return whether the stamp is the null stamp or not.
	 */
	public abstract boolean isNullStamp();
}