Sorting array with null values [duplicate]

Question

I have a program that allows user to delete an element from an array and I am trying to sort them in alphabetic order using compareTo(); through a for loop. However, the null values are giving me problems. For example an array with null values:

String[] myArray = {"Apple", "Banana", null, "Durian", null, null, "Grapes"};

When Java is comparing them and reads a null value, it would give me a NullPointerException.

Is there any way that I can sort this array with null values at the back? For example:

{"Apple", "Banana", "Durian", "Grapes", null, null, null}

I know that using Vectors can solve the problem but I am just curious if there is any way that I can just do it without changing my array to vectors.

With Guava, this is straightforward: Arrays.sort(array, Ordering.natural().nullsLast()) — Louis Wasserman
– Louis Wasserman, Commented Jan 25, 2013 at 3:22

Jeff Lockhart · Accepted Answer · 2014-06-10 23:18:07Z

28

try this

    Arrays.sort(myArray, new Comparator<String>() {
        @Override
        public int compare(String o1, String o2) {
            if (o1 == null && o2 == null) {
                return 0;
            }
            if (o1 == null) {
                return 1;
            }
            if (o2 == null) {
                return -1;
            }
            return o1.compareTo(o2);
        }});

it produces the required order

edited Jun 10, 2014 at 23:18

Jeff Lockhart

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answered Jan 25, 2013 at 4:27

Evgeniy Dorofeev

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AlexWien · Accepted Answer · 2013-01-25 02:40:04Z

7

write your own Comparator that accepts null values, and pass that comparator to the Arrays.sort() method

answered Jan 25, 2013 at 2:40

AlexWien

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