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
saveSelectionState(memento);
		saveScrollState(memento, fViewer.getTree());
		savePatternFilterState(memento);
		saveFilterState(memento);
		saveWorkingSetState(memento);
	}
	protected void saveFilterState(IMemento memento) {
		boolean showLibraries= getLibraryFilter().getShowLibraries();
		String show= "true"; 
		if (!showLibraries)
			show= "false"; 
		memento.putString(TAG_SHOWLIBRARIES, show);
		
		
		boolean showBinaries= getBinaryFilter().getShowBinaries();
		String showBinString= "true"; 
		if (!showBinaries)
			showBinString= "false"; 
		memento.putString(TAG_SHOWBINARIES, showBinString);
	}
	protected void savePatternFilterState(IMemento memento) {
		String filters[] = getPatternFilter().getPatterns();
		if(filters.length > 0) {
			IMemento filtersMem = memento.createChild(TAG_FILTERS);
			for (int i = 0; i < filters.length; i++){
				IMemento child = filtersMem.createChild(TAG_FILTER);
				child.putString(TAG_ELEMENT,filters[i]);
			}
		}
	}