When you serialize your nodes, you save them to disk so that when the application restarts, they can be used again in the application in the state that they were when the application shut down.

From Serialization and traversal in the NetBeans Javadoc:

''"If you need to store (serialize) a node for any reason, this is generally impossible due to the welter of Java-level references connecting it to the rest of the system. Rather, you must use a special serializable handle which represents the node by its position in the hierarchy, and permits finding the original node again after deserialization (if it still exists). To create a handle, just call Node.getHandle(), and to restore the node call Node.Handle.getNode().

Creation of a usable handle is implemented in AbstractNode, and you should not need to override it. However, note that a handle consists of a handle for the root node of the target node’s hierarchy together with a path (by system name) down to the target node; so if you are creating a root node, and want it or its children to be serializable, then you should create a specific implementation of Node.Handle capable of reconstructing your root from scratch, and return it from Node.getHandle().

The methods in NodeOp such as NodeOp.findPath(…​) may also be used for general-purpose navigation along the hierarchy, should this be necessary."''

Some concrete examples: