Bug 5774 Unpredicatable behaviour on double click in packages view
from EC: If you double click a file in the packages view, it opens the file (technically, compilation unit I believe) -- if not already open. However, if the file is already open, a single click selects it as the active editor tag; a double click expands its structure in the packages view. This is unpredictable behavior ;
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
}
		public void partClosed(IWorkbenchPart part) {
		}
		public void partDeactivated(IWorkbenchPart part) {
		}
		public void partOpened(IWorkbenchPart part) {
		}
	};
	
	private ITreeViewerListener fExpansionListener= new ITreeViewerListener() {
		public void treeCollapsed(TreeExpansionEvent event) {
		}
		
		public void treeExpanded(TreeExpansionEvent event) {
			Object element= event.getElement();
			if (element instanceof ICompilationUnit || 
				element instanceof IClassFile)
				expandMainType(element);
		}
	};
	
	public PackageExplorerPart() { 
	}
	/* (non-Javadoc)
	 * Method declared on IViewPart.
	 */
	public void init(IViewSite site, IMemento memento) throws PartInitException {
		super.init(site, memento);
		fMemento= memento;
	}