int		index;
int index = parent.getIndex(this) - 1;
	public DefaultMutableTreeNode getPreviousSibling() {		// Variables		int		index;		// Check for Parent		if (parent == null) {			return null;		} // if		// Get Index of this node		index = parent.getIndex(this);		// Check for Previous Sibling		index--;		if (index < 0) {			return null;		} // if		return (DefaultMutableTreeNode) parent.getChildAt(index);	} // getPreviousSibling()