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
if(state == null) {
			IPreferenceStore store= JavaPlugin.getDefault().getPreferenceStore();
			state= new Integer(store.getInt(TAG_LAYOUT));
		}
		if (state.intValue() == FLAT_LAYOUT)
			fIsCurrentLayoutFlat= true;
		else if (state.intValue() == HIERARCHICAL_LAYOUT)
			fIsCurrentLayoutFlat= false;
		else
			fIsCurrentLayoutFlat= true;
	}
	
	/**
	 * Returns the package explorer part of the active perspective. If 
	 * there isn't any package explorer part <code>null</code> is returned.
	 */
	public static PackageExplorerPart getFromActivePerspective() {
		IWorkbenchPage activePage= JavaPlugin.getActivePage();
		if (activePage == null)
			return null;
		IViewPart view= activePage.findView(VIEW_ID);
		if (view instanceof PackageExplorerPart)
			return (PackageExplorerPart)view;
		return null;	
	}
	
	/**
	 * Makes the package explorer part visible in the active perspective. If there
	 * isn't a package explorer part registered <code>null</code> is returned.