Question

I have some questions regarding arrays in java:

How many objects are created in the following expressions?

(a) new int[0] : There is one object created, an array of size 0.???

(b) new int[2][2] : There is one object created, an array with 2 rows and columns.???

(c) new int[2][] : There is no object created???

I was wondering if my solutions next to the expressions are correct. If not, hopefuly you can help and give me some explanation about them. I don’t really get what im supposed to do.

Thanks in advance!

Answer 1

new int[0]

Yes this is an empty array, one object is created.

    int[] emptyArray = new int[0];
    System.out.println(emptyArray.length); // Outputs 0

new int[2][2]

Yes this creates and array with 2 rows and columns, 3 objects are created.

    int[][] bar = new int[2][2];
    System.out.println(bar.getClass()); // Outputs class [[I
    int[] bar1 = bar[0];
    System.out.println(bar1.getClass());  // Outputs class [I
    int[] bar2 = bar[1];
    System.out.println(bar2.getClass());  // Outputs class [I

new int[2][]

Java supports jagged arrays. This means when you create int[2][] this means you have an array of various sized int[]. Only 1 object is created here.

    int[][] foo = new int[2][];
    System.out.println(foo[0]);  // Outputs null
    System.out.println(foo[1]);  // Outputs null
    foo[0] = new int[10];
    foo[1] = new int[5];