Bug 15586 Warn the user when a project without the Java nature is opened
When opening a closed project that doesn't have the Java nature when opened, then we should inform the user that the opened project will not appear in the packages view.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/OpenProjectAction.java
IResourceDelta projDelta = projDeltas[i];
				if ((projDelta.getFlags() & IResourceDelta.OPEN) != 0) {
					setEnabled(hasCloseProjects());
					return;
				}
			}
		}
	}
		
	private Object[] getClosedProjects() {
		IProject[] projects= ResourcesPlugin.getWorkspace().getRoot().getProjects();
		List result= new ArrayList(5);
		for (int i = 0; i < projects.length; i++) {
			IProject project= projects[i];
			if (!project.isOpen())
				result.add(project);
		}
		return result.toArray();
	}
	
	private boolean hasCloseProjects() {
		IProject[] projects= ResourcesPlugin.getWorkspace().getRoot().getProjects();
		for (int i = 0; i < projects.length; i++) {
			if (!projects[i].isOpen())
				return true;
		}
		return false;
	}
}