Cannot make an array of Nodes

Question

I get the following error when trying to create an array of Nodes:

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [LSkipList$Node;

This is my code:

    public class Node {
      Key key;
      Value val;
      Node[] next;

      //constructor
      public Node(Key k, Value v) {
        key = k;
        val = v;
        next = (Node[])new Object[MAX_LEVEL];

      }
    }

Why are you making a new array of objects and casting it to an array of nodes instead of just making an array of nodes? — Paul
– Paul, Commented Dec 8, 2018 at 1:05

ruakh · Accepted Answer · 2018-12-08 01:11:12Z

1

This:

new Object[MAX_LEVEL]

means "a new array of type Object[] and size MAX_LEVEL where every element is null".

This:

(Node[])new Object[MAX_LEVEL]

means the same, plus "but check if it has type Node[]; if not, raise ClassCastException". But that's redundant, because you just created the array with type Object[], so you know it doesn't have type Node[]. So it will always raise ClassCastException.

Instead, you need to write this:

new Node[MAX_LEVEL]

which means "a new array of type Node[] and size MAX_LEVEL where every element is null".

answered Dec 8, 2018 at 1:11

ruakh

185k29 gold badges292 silver badges324 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Cannot make an array of Nodes

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related