Java: Change an objects value without changing all

Question

This is probably a noob question, but i just don't get it.

I am trying to implement A* pathfinding in my game. I was following this tutorial and the code in the AstarPathfinder.java. But instead of instantiating the AStarPathfinder class and having an 2D Array for all Nodes i made a static method, to which i pass my 2D Array (the Level/World), start and end Node. Cause of this i always have to store the current and the next Node in a Node next and Node current. I then add them to the open or closed list (depends on where they belong) and change the x and y value (position) of the Node with their setter method, to have the next node.

After a few minutes of debuging i noticed that this (ofc) changes also the value of the node inside the openList and closedList. To prevent this i can simply call next = new Node(int x, int y) instead of only setting the values, but as my Pathfinding is running every few render loops it would mess up garbage collection and cost a lot of performance. So i am looking for a possibility to have one Node variable, which i can instantiate once with default constructor, and then change its value without changing its value in the list.

Is that possible somehow?

Answer 1

What you're looking for is not possible. You only have one instance of a Node object, with pointers to that object in multiple locations. You need to make new Node instances.

it would mess up garbage collection and cost a lot of performance

If you haven't done performance testing and shown that this is an unacceptable bottleneck, you should not assume this.

Answer 2

While this is not a direct answer to your question, hopefully it will help you make a good decision

The JVM has become very good at re-using objects and you should generally not be afraid to use the new keyword.

For more detailed reading, see should-we-avoid-object-creation-in-java