Bug 32224 [Show In]Back-linking doesn't work for .class files in jars
Build 20030218 1. Enable back-linking in Package Explorer 2. Open Object (in rt.jar) Observe: An editor on Object.class opens (it shows the attached source). However Object.class is not shown in Package Explorer Note that Alt-Shift-s->Package Explorer doesn't work either.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
return fViewer;
	}
	
	boolean isExpandable(Object element) {
		if (fViewer == null)
			return false;
		return fViewer.isExpandable(element);
	}
	void setWorkingSetName(String workingSetName) {
		fWorkingSetName= workingSetName;
	}
	
	/**
	 * Updates the title text and title tool tip.
	 * Called whenever the input of the viewer changes.
	 */ 
	void updateTitle() {		
		Object input= fViewer.getInput();
		String viewName= getConfigurationElement().getAttribute("name"); 
		if (input == null
			|| (input instanceof IJavaModel)) {
			setTitle(viewName);
			setTitleToolTip(""); 
		} else {
			String inputText= JavaElementLabels.getTextLabel(input, AppearanceAwareLabelProvider.DEFAULT_TEXTFLAGS);
			String title= PackagesMessages.getFormattedString("PackageExplorer.argTitle", new String[] { viewName, inputText }); 
			setTitle(title);
			setTitleToolTip(getToolTipText(input));
		} 
	}