How can I check whether an array is null / empty?

Question

There's a key difference between a null array and an empty array. This is a test for null.

int arr[] = null;
if (arr == null) {
  System.out.println("array is null");
}

"Empty" here has no official meaning. I'm choosing to define empty as having 0 elements:

arr = new int[0];
if (arr.length == 0) {
  System.out.println("array is empty");
}

An alternative definition of "empty" is if all the elements are null:

Object arr[] = new Object[10];
boolean empty = true;
for (int i=0; i<arr.length; i++) {
  if (arr[i] != null) {
    empty = false;
    break;
  }
}

or

Object arr[] = new Object[10];
boolean empty = true;
for (Object ob : arr) {
  if (ob != null) {
    empty = false;
    break;
  }
}

ArrayUtils.isNotEmpty(testArrayName) from the package org.apache.commons.lang3 ensures Array is not null or empty

Look at its length:

int[] i = ...;
if (i.length == 0) { } // no elements in the array

Though it's safer to check for null at the same time:

if (i == null || i.length == 0) { }

Method to check array for null or empty also is present on org.apache.commons.lang:

import org.apache.commons.lang.ArrayUtils;

ArrayUtils.isEmpty(array);