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
import org.eclipse.jface.dialogs.ProgressMonitorDialog;
import org.eclipse.jface.operation.IRunnableWithProgress;
import org.eclipse.jface.util.Assert;
import org.eclipse.core.resources.IProject;
import org.eclipse.core.resources.IResourceChangeEvent;
import org.eclipse.core.resources.IResourceChangeListener;
import org.eclipse.core.resources.IResourceDelta;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.SubProgressMonitor;
import org.eclipse.ui.IWorkbenchSite;
import org.eclipse.ui.dialogs.ElementListSelectionDialog;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.actions.ActionMessages;
import org.eclipse.jdt.internal.ui.util.ExceptionHandler;
import org.eclipse.jdt.ui.JavaElementLabelProvider;
/**
 * Action to open a closed project. Action presents a dialog from which the
 * user can select the projects to be opened.
 * 
 * @since 2.0
 */
public class OpenProjectAction extends Action implements IResourceChangeListener {
	
	private IWorkbenchSite fSite;
	/**
	 * Creates a new <code>OpenProjectAction</code>.