Bug 4240 Can't edit class path entry (1GKEPIF)
There is no way to edit an existing entry for a library on the Java Build Path project properties page (other than editing the .classpath file directly). NOTES: EG (9/22/2001 11:42:11 AM) this is particularly annoying for variables. we should have an Edit button when a variable is selected.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/SourceContainerWorkbookPage.java
return null;
	}
	
	/**
	 * Asks to change the output folder to 'proj/bin' when no source folders were existing
	 */ 
	private void askForChangingBuildPathDialog() {
		IPath outputFolder= new Path(fOutputLocationField.getText());
		if (outputFolder.segmentCount() == 1) {
			String outputFolderName= JavaBasePreferencePage.getOutputLocationName();
			IPath newPath= outputFolder.append(outputFolderName);
			String title= NewWizardMessages.getString("SourceContainerWorkbookPage.ChangeOutputLocationDialog.title"); 
			String message= NewWizardMessages.getFormattedString("SourceContainerWorkbookPage.ChangeOutputLocationDialog.message", newPath); 
			if (MessageDialog.openQuestion(getShell(), title, message)) {
				fOutputLocationField.setText(newPath.toString());
			}
		}
	}
	
			
			
	private CPListElement[] chooseSourceContainers() {	
		Class[] acceptedClasses= new Class[] { IFolder.class };
		TypedElementSelectionValidator validator= new TypedElementSelectionValidator(acceptedClasses, true);
			
		acceptedClasses= new Class[] { IFolder.class };
		ViewerFilter filter= new TypedViewerFilter(acceptedClasses, getExistingContainers());	
		
		ILabelProvider lp= new WorkbenchLabelProvider();
		ITreeContentProvider cp= new WorkbenchContentProvider();