String sorting null values

If you are using Java 8, you can easily build the comparator you need:

Arrays.sort(stringArray, Comparator.nullsLast(Comparator.naturalOrder()));

But if you not using java 8 you can have a comparator like below

public class StringNullComparator implements Comparator<String> {
    public int compare(String stringOne, String stringTwo) {
        if (stringOne != null && stringTwo != null)
            return stringOne.compareTo(stringTwo);
        return (stringOne == stringTwo)?0:(stringOne==null? 1 : -1);
    }
}

And you can use at stated below

Arrays.sort(stringArray, new StringNullComparator());   

Custom Comparator to pass to sort:

public class StringComparator implements Comparator<String> {
    public int compare(String s1, String s2) {
        if (s1 != null && s2 != null)
            return s1.compareTo(s2);
        return (s1 == null) ? 1 : -1;
    }
}

then:

Collectios.sort(list, new StringComparator());