Check if Java object is Collection, Array or String and empty

Question

I've got this method at the moment that I am trying to refactor.

public static boolean isEmpty(Object value) {
    boolean empty = false;
    if (value instanceof String && ((String) value).isEmpty()) {
        empty = true;
    } else if (value instanceof List && ((List<?>) value).isEmpty()) {
        empty = true;
    } else if (value instanceof String[] && ArrayUtils.isEmpty((String[]) value)) {
        empty = true;
    } else if (value == null) {
        empty = true;
    }

    return empty;
}

Is there an obviously better way to do this that I am missing?

I know I could put all the conditions on one if statement using chained || statements, but I don't really see how that is better than what I've got now.

Answer 1

As mentioned in deHaar's answer, the code can be improved by using if-return combinations.

You should however generalize your code a bit more, e.g. support all array types, not just string arrays, and support all collection types, not just lists.

Similarly, String implements an interface named CharSequence, so support that instead. That way the code will support classes like StringBuilder and StringBuffer too.

public static boolean isEmpty(Object value) {
    if (value == null)
        return true;
    if (value instanceof CharSequence) // String, StringBuilder, StringBuffer, ...
        return ((CharSequence) value).isEmpty();
    if (value instanceof Collection) // List, Set, Queue, Deque, ...
        return ((Collection<?>) value).isEmpty();
    if (value instanceof Map)
        return ((Map<?,?>) value).isEmpty();
    if (value.getClass().isArray()) // All array types
        return (Array.getLength(value) == 0);
    return false;
}

Code was modified to to use pure built-in methods, i.e. to not rely on ArrayUtils.

UPDATED: Added support for primitive arrays.

The above implementation is a close match to the JSP EL empty operator:

The empty operator is a prefix operator that can be used to determine if a value is null or empty.

To evaluate empty A

• If A is null, return true
• Otherwise, if A is the empty string, then return true
• Otherwise, if A is an empty array, then return true
• Otherwise, if A is an empty Map, return true
• Otherwise, if A is an empty Collection, return true
• Otherwise return false