Someone

public Object[] getElements(Object parent) {
	if (parent instanceof Object[]) {
			return (Object[]) parent;
	} else {
		try {
			return ((IProject) parent).members();
		} catch (CoreException e) {
			return new String[] { "FAIL" };
		}
	}
}

public Object getParent(Object child) {
	if (child instanceof IProject) {
		return null;
	}
	return ((IResource) child).getParent();
}

public Object[] getChildren(Object parent) {
	if (parent instanceof IProject) {
		try {
			return ((IProject) parent).members();
		} catch (CoreException e) {}
	}
	return null;
}

public boolean hasChildren(Object parent) {
	return parent instanceof IProject;
}