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How to write a generic isEmpty method which can check for null, empty?

I am writing a utility method which can check for empty and null string, or collection or an object or any general types -

public static boolean isEmpty(Object obj) {
    if (obj == null)
        return true;
    if (obj instanceof Collection)
        return ((Collection<?>) obj).size() == 0;

    // is below line expensive?
    final String s = String.valueOf(obj).trim();

    return s.length() == 0 || s.equalsIgnoreCase("null");
}

How can I make my above method efficient, since above isEmpty method will be called multiple times from the application which is very performance critical?

I am suspecting below line will be expensive because of heavy toString methods and it will create temporary garbage as well that might cause GC and slow down the performance?

final String s = String.valueOf(obj).trim();

Update:-

I have separated isEmpty method for each type now. Below is what I got after simplifying the above isEmpty method.

public static boolean isEmpty(Object obj) {
    if (obj == null) {
        return true;
    }
    return false;
}

public static boolean isEmpty(Collection<?> value) {
    if (value == null || value.isEmpty()) {
        return true;
    }
    return false;
}

public static boolean isEmpty(String value) {
    if (value == null || value.isEmpty()) {
        return true;
    }
    return false;
}

Update 2:-

If I need to check for map null or empty, should I keep both collection isEmpty and Map isEmpty method both or Collection isEmpty method will be fine for that?

public static void main(String[] args) {

    Map<String, String> hello = new HashMap<String, String>();
    System.out.println(isEmpty(hello));

    Map<String, HashMap<Integer, String>> primary = new HashMap<String, HashMap<Integer, String>>();
    System.out.println(isEmpty(primary));

}

public static boolean isEmpty(Collection<?> value) {
    return value == null || value.isEmpty();
}

public static boolean isEmpty(Map<?, ?> value) {
    return value == null || value.isEmpty();
}
like image 599
john Avatar asked Jul 05 '14 22:07

john


2 Answers

This sounds like a bad design to me. Null is null, empty is empty, if it's a string it's a string, and so on. Don't try to jam everything up in one method. It's bad for maintainability and readability.

if (str == null || str.isEmpty())
    ...

and

if (coll == null || coll.isEmpty())

are both perfectly fine.

Personally however, I try to never ever equate null with an empty string or empty collection. I think it's a bad practice. A null collection is no collection at all, an empty collection is in fact still a collection. You can avoid many if (coll == null) checks by keeping a collection non-null. If you're worried about memory consumption, use use Collections.emptySet et al.


That being said, if you still want to go in this direction, I'd suggest you use plain method overloading and create one isEmpty(Collection<?> coll) and one isEmpty(String str) to avoid instanceof and casting.


Regarding your edit:

Don't do for instance

if (value == null || value.isEmpty()) {
    return true;
}
return false;

just do

return value == null || value.isEmpty();
like image 191
aioobe Avatar answered Oct 21 '22 02:10

aioobe


For collections, you'll want to use isEmpty() instead of size(). For some collection types (such as LinkedList), size() is more expensive than isEmpty().

like image 2
Steve Kuo Avatar answered Oct 21 '22 00:10

Steve Kuo