CODEWITHSUNDEEP
javadata-structuresnodes
salty_coffee
salty_coffee

Reputation: 631

Node class for binary tree. Getting stackoverflow error

Im getting a Stackoverflow error in my node class for a tree data structure. I am aware of the cause, however I cannot seem to fix it.

public class Node {
    Node right;
    Node left;
    String element;
    Node parent;

    public Node(){  
        right = new Node();
        left = new Node();
    }
}

because Im constructing new Nodes within the constructor, I get a stack overflow. How can I structure my constructor and avoid this error?

Upvotes: 0

Views: 612

Answers (3)

shizhz
shizhz

Reputation: 12521

Don't new Node itself in its constructor, it'll never end till stackoverflow or heap out of memory, you could do it:

  • Pass left, right to constructor:

Code: 

public class Node {
    Node right;
    Node left;
    String element;
    Node parent;

    public Node(Node left, Node right){  
        this.left = left;
        this.right = right;
    }
}
  • With setter:

Code: 

public class Node {
    Node right;
    Node left;
    String element;
    Node parent;

    public Node(){  
    }

   public void setLeft(Node left) {
       this.left = left;
   }


   public void setRight(Node right) {
       this.right = right;
   }
}

Upvotes: 1

Codor
Codor

Reputation: 17605

You should delete the recursive constructor calls as follows.

    public Node(){  
        right = null;
        left = null;
    }

The assembly of a specific tree should be done by assigning the children from perhaps outside the class or via getter and setter functions.

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533660

You can create the Nodes on demand when they actually exist.

public class Node {
    Node left, right; // created as required
    String element;
    Node parent;

    public Node(Node parent, String element) {
        this.parent = parent;  
        this.element = element; // if you don't have an element you don't need a Node.
    }
}

Note: most likely you don't need the parent field, most implementations don't use it.

public class Node {
    Node left, right; // created as required
    String element;

    public Node(String element) {
        this.element = element; // if you don't have an element you don't need a Node.
    }

    public void setLeft(Node left) { this.left = left; }
    public void setRight(Node right) { this.right = right; }
}

e.g.

 Node d = new Node("d");
 d.setLeft(new Node("a"));
 d.setRight(new Node("z"));

Upvotes: 3

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