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
project.open(monitor);
				monitor= null;
			}
		} finally {
			if (monitor != null) {
				monitor.done();
			}
		}
	}
	public static void addJavaNature(IProject project, IProgressMonitor monitor) throws CoreException {
		if (monitor != null && monitor.isCanceled()) {
			throw new OperationCanceledException();
		}
		if (!project.hasNature(JavaCore.NATURE_ID)) {
			IProjectDescription description = project.getDescription();
			String[] prevNatures= description.getNatureIds();
			String[] newNatures= new String[prevNatures.length + 1];
			System.arraycopy(prevNatures, 0, newNatures, 0, prevNatures.length);
			newNatures[prevNatures.length]= JavaCore.NATURE_ID;
			description.setNatureIds(newNatures);
			project.setDescription(description, monitor);
		} else {
			monitor.worked(1);
		}
	}
	
	public void configureJavaProject(IProgressMonitor monitor) throws CoreException, OperationCanceledException {
		
		flush(fClassPathList.getElements(), getOutputLocation(), monitor);
		initializeTimeStamps();