Creating an array of Deques

Question

I need to create and use an array of Deques, something like the following

Deque<Point>[] saved = new LinkedList<Point>[12];

This code results in an error because Java doesn't allow you to create generic arrays of Deques. Is there a way to set up the array of Deques so I can access each individual Deque when I need to?

I also tried:

Deque<Point>[] saved;
//....
for(int i = 0;i<12;i++)
{
     saved[i] = new LinkedList<Point>;
}

which returns a NullPointerException. How can I create this array?

@Jens I'm afraid not, I get the same "Cannot create a generic array of Deque<Point>" — imulsion
– imulsion, Commented Mar 16, 2017 at 13:09

sdgfsdh · Accepted Answer · 2017-03-16 13:13:56Z

2

You need to initialize saved to an ArrayList:

// Note that saved has a size defined at construction, 
// which makes this efficient. 
final List<Deque<Point>> saved = new ArrayList<Deque<Point>>(12);
for (int i = 0; i < 12; i++) {
   saved.add(new LinkedList<Point>());
}

edited Mar 16, 2017 at 13:13

answered Mar 16, 2017 at 13:09

sdgfsdh

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4 Comments

imulsion Over a year ago

Doesn't work I'm afraid, I get the same complaint about not being able to create a generic array of Deque<Point>

sdgfsdh Over a year ago

Ah, of course. An ArrayList with a size defined at construction should work well. Updated the answer.

VGR Over a year ago

@imulsion There is no array creation in that code. What line of code is giving you that error?

imulsion Over a year ago

The updated solution worked perfectly. Thanks very much for your help.

Youcef LAIDANI · Accepted Answer · 2017-03-16 13:23:20Z

1

Why you don't use ArrayDeque?

You can use this :

ArrayDeque arr = new ArrayDeque<Point>(12);

Or this :

LinkedList l = new LinkedList<Point>();
ArrayDeque arr = new ArrayDeque(l);

There are a good tutorial here Java.util.ArrayDeque Class

edited Mar 16, 2017 at 13:23

answered Mar 16, 2017 at 13:16

Youcef LAIDANI

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1 Comment

Maximilien Belinga Over a year ago

I was thinking about the same thing. ArrayDeque is a Fast Deque Operations Using an Array.

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