Passing int[][] as generic parameter

Question

public static <T> void func1(T[][] arr) {
    ...
}

public static <T> void func2(T[] arr) {
    ...
}

I'm trying to pass a 2-dimensional array, int[][] arr.

I cannot use func1(arr) , but I can use func2(arr)

Can someone explain me how this works?

score 25 · Answer 1 · answered Nov 17 '18 at 21:14

25

T[] represents an array of some generic object. Any array type (including int[]) is an object. Therefore, int[][] is a valid T[] when T = int[].

However, because int is not an object, int[][] is not a valid T[][].

answered Nov 17 '18 at 21:14

Joe C

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4

To expand on this, you could change it to Integer[][] arr; and it should work. – LadyCailin Nov 17 '18 at 22:28
3

@LadyCailin true, but in most cases when you need multi-dimensional arrays, it is really bad idea to use wrapper types – user1643723 Nov 18 '18 at 06:25

Taher A. Ghaleb · Answer 2 · 2018-11-18T00:55:14.053

2

If you you use Integer instead of int, you should be able to:

call func1 with Integer[][] arr
call func2 with Integer[] arr or Integer[][] arr

edited Nov 18 '18 at 00:55

answered Nov 17 '18 at 23:56

Taher A. Ghaleb

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Passing int[][] as generic parameter

2 Answers2