Java中零长度的数组

Question

Below code

public class Example {
    static int[] member;
    public static void main(String[] args) {
        int[] ic = new int[0];
        if (ic == null){
            System.out.println("ic is null");
        }
        System.out.println(ic);  // [I@659e0bfd
        if(member == null){
            System.out.println("member is null");
        }
    }
}

It is obvious that elements can't be added in zero length array.

What does ic point to, if ic is not null ?

As per below diagram, Is ic pointing to memory location 659e0bfd (which is empty)?

Answer 1

What does ic point to, if it is not null?

It points an empty array of zero capacity. Arrays are reference types and memory space is allocated for them like any other reference type.

Answer 2

Imagine an array as a box. You can declare a box with some capacity, say 3

int[] x = new int[3];

and you'll get this box: [_,_,_] . You can fill it with some numbers

x[1] = 9;

to get [_,9,_] . What you did, instead, is declaring an zero capacity box

int[] x = new int[0];

to get this: [] . And guess what happens if you try to add an element to it? You cannot.

So, to answer your question, what does ic point to? Your empty (and zero capacity) box.

Answer 3

ic refers to an empty array instance. It contains no elements ( ic[i] would throw ArrayIndexOutOfBoundsException for each value of i ), but it's not null.