Getting ClassCastException when trying to create an array of an inner class type

Question

I'm trying to make a linked-list representation of Deque , each node of the linked list is defined by an instance of the inner class Node , but I'm getting this :

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [LRandomizedQueue$Node;

I dony know how to work this out. This is what i had:

private class Node {
        Item item;
        Node next;
        Node prev;
    }

    @SuppressWarnings("unchecked")
    private Node[] nd = (Node[]) new Object[100];

Can someone please tell me what i'm doing wrong , and help me figure this out ? Thanks a lot for your time.

Edit: It seems i had things confused with creating a generic array vs an array of an inner class. Thanks a lot for the replies.

You're creating an Object[] and trying to cast it to a Node[]. Would you expect Node node = (Node) new Object() to work? — yshavit
– yshavit, Commented Sep 11, 2013 at 8:07
Always quite a good idea not to have @SuppressWarnings("unchecked") — Scary Wombat
– Scary Wombat, Commented Sep 11, 2013 at 8:07

Matthew Mcveigh · Accepted Answer · 2013-09-11 08:06:51Z

2

You're creating an array of Objects and then trying to cast them to an array of Nodes; you need to create an array of Nodes

try

private Node[] nd = new Node[100];

answered Sep 11, 2013 at 8:06

Matthew Mcveigh

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Subhrajyoti Majumder · Accepted Answer · 2013-09-11 08:08:17Z

1

private Node[] nd = (Node[]) new Object[100];

It Should throws ClassCastException. It is not possible to cast array object to Node object.

Create like -

Node[] nd = new Node[100];

answered Sep 11, 2013 at 8:08

Subhrajyoti Majumder

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1 Comment

Marcin Łoś Over a year ago

It's worth noting it's possible the other way around, while it (arguably) shouldn't

Narendra Pathai · Accepted Answer · 2013-09-11 08:08:43Z

1

private Node[] nd = (Node[]) new Object[100];

Why would you do this?

You are clearly casting wrong objects to wrong reference types.

The object is of type Object[] and you are casting it to Node[], which will never work.

Do this instead.

Node[] nd = new Node[size];

answered Sep 11, 2013 at 8:08

Narendra Pathai

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No Idea For Name · Accepted Answer · 2013-09-11 08:12:20Z

0

you are creating an object array and try to cast it to Node array. this kind of casting is not allowed because object is not a Node

you can do

Node[] nd = new Node[100];

if you need an array of Node or

Object[] nd = new Object[100];

if you need just an array of objects

for future, you should know that usually when you get ClassCastException that means you have tried to cast a class to other class when the case is invalid, and should try to understand the hierarchy of the objects

answered Sep 11, 2013 at 8:12

No Idea For Name

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VishalDevgire · Accepted Answer · 2013-09-11 08:15:25Z

0

You essentially need : private Node[] nd = new Node[100];

Because Arrays are themselves objects, since new Object[100] will return an object of array class you can't cast it into some other class object which here is Node.

edited Sep 11, 2013 at 8:15

answered Sep 11, 2013 at 8:10

VishalDevgire

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