an object where it has a parent and an action and each parent has a parent and an action

Question

How can I do this in Java

public class State implements Comparable<State> {
    //other attbs;
    State parent;
    String actionFromParent;
// other code
}

where x is an object of type State and each parent itself has an action from parent. I want to do this until I have actionFromParent == null.

I don't know how many parents there are. I'm using this to print the path for A* algorithm. I'm stuck at printing the path after x (state currentnode) satisfies the goal, I print all actionfromparents of its child nodes.

System.out.println(x.actionFromParent);
System.out.println(x.parent.actionFromParent);
System.out.println(x.parent.parent.actionFromParent);
System.out.println(x.parent.parent.parent.actionFromParent);
.....
until  (x.parent.parent.parent.....parent.actionFromParent == null)

Answer 1

You can use a while loop or a recursive function.

With a while loop:

State x = theState;
while (x != null && x.actionFromParent != null) {
    System.out.println(x.actionFromParent);
    x = x.parent;
}

With a recursive function:

public static void printActionsFromParent(State x) {
    if (x != null && x.actionFromParent != null) {
        System.out.println(x.actionFromParent);
        printActionsFromParent(x.parent);
    }
}