Bug 120544 [build path] Editing external source folder does not persist
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
public boolean hasChangesInClasspathFile() {
		IFile file= fCurrJProject.getProject().getFile(".classpath"); 
		return fFileTimeStamp != file.getModificationStamp();
	}
	
	public void initializeTimeStamps() {
		IFile file= fCurrJProject.getProject().getFile(".classpath"); 
		fFileTimeStamp= file.getModificationStamp();
		fUserSettingsTimeStamp= getEncodedSettings();
	}
	
	
	private ArrayList getExistingEntries(IClasspathEntry[] classpathEntries) {
		ArrayList newClassPath= new ArrayList();
		for (int i= 0; i < classpathEntries.length; i++) {
			IClasspathEntry curr= classpathEntries[i];
			newClassPath.add(CPListElement.createFromExisting(curr, fCurrJProject));
		}
		return newClassPath;
	}
	
	
	
	/**
	 * @return Returns the Java project. Can return <code>null<code> if the page has not
	 * been initialized.
	 */
	public IJavaProject getJavaProject() {
		return fCurrJProject;