CODEWITHSUNDEEP
javadictionary
Pravat Panda
Pravat Panda

Reputation: 1090

AbstractMap's containsValue() method implementation

containsValue() is implemented in AbstractMap class as below:

public boolean containsValue(Object value) {
    Iterator<Entry<K,V>> i = entrySet().iterator();
    if (value==null) {
        while (i.hasNext()) {
            Entry<K,V> e = i.next();
            if (e.getValue()==null)
                return true;
        }
    } else {
        while (i.hasNext()) {
            Entry<K,V> e = i.next();
            if (value.equals(e.getValue()))
                return true;
        }
    }
    return false;
}

What if the implementation had been as below:

public boolean containsValue(Object value) {
    Iterator<Entry<K,V>> i = entrySet().iterator();
    while (i.hasNext()) {
        Entry<K,V> e = i.next();
        if (e.getValue().equals(value))
            return true;
    }
    return false;
}

Is there any performance improvement by implementing a null specific checking in the original method?

Upvotes: 1

Views: 379

Answers (1)

Eran
Eran

Reputation: 393771

In your suggested implementation, e.getValue().equals(value) would throw a NullPointerException if e.getValue() is null, which is why you must have separate logic to handle null.

It's not a matter of performance. It's a matter of correctness.

Upvotes: 4

Related Questions