Bug 17566 Browsing Java src not on class path
When browsing Java src which is not on the classpath it is annoying to have millions of Quickfix light bulbs and error indicators. I suggest to disable this feature and have a special icon in the editor tab to indicate that the source file is not on the classpath and therefore behaves differently in certain operations (search, quickfix, etc.)
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
/**
	 * Saves the content of the given document to the given element.
	 * This is only performed when this provider initiated the save.
	 * 
	 * @param monitor the progress monitor
	 * @param element the element to which to save
	 * @param document the document to save
	 * @param overwrite <code>true</code> if the save should be enforced
	 */
	public void saveDocumentContent(IProgressMonitor monitor, Object element, IDocument document, boolean overwrite) throws CoreException {
		
		if (!fIsAboutToSave)
			return;
		
		if (element instanceof IFileEditorInput) {
			
			IFileEditorInput input= (IFileEditorInput) element;
			InputStream stream= new ByteArrayInputStream(document.get().getBytes());
			
			IFile file= input.getFile();
			file.setContents(stream, overwrite, true, monitor);
		}
	}
	
	/**
	 * Returns the underlying resource for the given element.
	 * 
	 * @param the element
	 * @return the underlying resource of the given element
	 */