Bug 31683 Show In doesn't work for class file in rt.jar
I20030611 - create Test project that uses Jar container - open NumberFormat.class - activate Show In... and choose Package Explorer Observe: NumberFormat.class doesn't get revealed.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
/**
 	 * Returns the TreeViewer.
 	 */
	public TreeViewer getTreeViewer() {
		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);