Compiler says "Cannot create a generic array" although array isn't generic [duplicate]

Question

I created the class Queue with

import java.util.LinkedList;
public class Queue <T>{
        private LinkedList<T> list;

        public Queue() {
            list = new LinkedList<>();
        }

        ...
}

I also created the class Cinema, which has a private field of an array of Queue<String>.

public class Cinema {
    private Queue<String>[] arr;
    
    public Cinema() {
        arr = new Queue<String>[10];
        for (int i = 0; i < 10; i++)
            arr[i] = new Queue<String>();
    }

        ...
}

However, the line arr = new Queue<String>[10]; throws a compilation error, saying Cannot create a generic array of Queue<String>. But as I understand it the array isn't generic, as its generic type is defined to be String.

When I change the line to

arr = new Queue[10];

the code works again, although it still gives me a warning saying Type safety: The expression of type Queue[] needs unchecked conversion to conform to Queue<String>[]. So I don't understand why the original doesn't work.

The short answer is that arrays and generics just never mix well. — Louis Wasserman
– Louis Wasserman, Commented Jan 30, 2023 at 17:11

rzwitserloot · Accepted Answer · 2023-01-30 17:11:12Z

0

But as I understand it the array isn't generic, as its generic type is defined to be String.

Different meanings of the same word. What the compiler means is: There are <> and/or type vars involved anywhere in the array type. Which you can't do.

Arrays are low-level constructs that you don't use except for classes that define new collection concepts. You aren't doing that here. Ditch the array, make a List<Queue<String>> instead.

If you insist on using arrays, you're doing it: arr = new Queue[10]. Yes, this gets a warning. The only thing you can do is live with it, or use @SuppressWarnings. Arrays and generics don't mix very well. Hence, don't - use List<Queue<String>> instead.

answered Jan 30, 2023 at 17:11

rzwitserloot

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