如何在ArrayList中存储2D Integer数组？

Question

I have this defined: List<Integer[][]> listOfInteger= new ArrayList<>();

How do I insert data into it?

I have tried

listOfInteger.add(new Integer[][](1,2));

and

List<Integer[][]> listOfInteger= Arrays.asList(new Integer({1, 2)});

But none works

Answer 1

The short way is this:

listOfInteger.add(new Integer[][] {{1, 2}, {1, 3}, {5, 7}});

But you could also just create the array and then fill it one by one.

Answer 2

You got confused by the dimensions you have defined an one dimensional ArrayLists which contains two-dimensional arrays as elements.

    List<Integer[][]> listOfInteger = new ArrayList<Integer[][]>();
    // long version
    Integer[][] array2d = new Integer[2][2];
    array2d[0][0] = 3;
    array2d[0][1] = 2;
    array2d[1][0] = 4;
    array2d[1][1] = 2;
    listOfInteger.add(array2d);
    // short version
    listOfInteger.add(new Integer[][] { { 3, 2 }, { 4, 2 } });

After this operations your arrayList will contain two arrays, which contain integers with the same value

Answer 3

Have you tried the "double brace initialization"?

List<Integer[][]> listOfInteger= new ArrayList() {{
    add(new Integer[][] { { 3, 2 }, { 4, 2 } });
    add(new Integer[][] { { 3, 2 }, { 4, 2 } });
    add(new Integer[][] { { 3, 2 }, { 4, 2 } });
}};

You can do this at the class level outside of methods.