Question

I’m quite new to Java and having an issue checking null element in integer array.
I’m using Eclipse for editor and the line that checks null element is showing error:

Line that complains:

if(a[i] != null) {

Error msg from Eclipse:

The operator != is undefined for the argument type(s) int, null

In PHP, this works without any problem but in Java it seems like I have to change the array type from integer to Object to make the line not complain (like below)

Object[] a = new Object[3];

So my question is if I still want to declare as integer array and still want to check null,
what is the syntax for it?

Code:

public void test() {
        int[] a = new int[3];
        for(int i=0; i<a.length; i++) {
            if(a[i] != null) { //this line complains...
                System.out.println('null!');
            }
        }
    }

Answer 1

In Java, an int is a primitive type and cannot be null. Objects, however, are stored as references, so if you declare an object reference but do not make a new object, the reference will be null.

Integers are object wrappers around ints, meaning they can be null.

public void test() {
        Integer[] a = new Integer[3];
        for(int i=0; i<a.length; i++) {
            if(a[i] != null) { //should now compile
                System.out.println('null!');
            }
        }
    }