How to retain information using a recursion in Java

Question

Basically, every time I recurse, I reset the variable "path," but I need to keep that information. Also, I cannot pass it as a parameter. Is there a way to do this?

Here is the code I have now:

public List<Person> getDiseaseRouteTo(Person c){

    List<Person> path = new LinkedList<Person>();

    if (this.root == c) {
        path.add(c);
        } else if (this.root != c) {
            path.add(this.root);
            for (DiseaseTree child: this.getChildren()) {
                if (child.contains(c)) {
                    path.add(child.getRoot());
                    return child.getDiseaseRouteTo(c);
                }
            }
        }
        return path;
    }

Answer 1

Also, I cannot pass it as a parameter.

You can always create a private helper method where you can pass it:

public List<Person> getDiseaseRouteTo(Person c) {
    List<Person> path = new LinkedList<Person>();
    return getDiseaseRouteTo(c, path);
}

private List<Person> getDiseaseRouteTo(Person c, List<Person> path) {
    // ...
}

Answer 2

You are creating a new instance of LinkedList every time you invoke the method.

You can create the path variable elsewhere, outside the scope of the getDiseaseRouteTo method, like janos suggested.