What is difference between isEmpty() and size() for hashmap if used under if condition?

Question

I have to deal with NullPointerException which is occurring on Hashmap. Shall I use map.isEmpty() or (map.size() > 0) inside if condition?

Which one is better?

Answer 1

Here are the implementations for size() and isEmpty() in the HashMap class:

public int size() {
    return size;
}

public boolean isEmpty() {
    return size == 0;
}

So, HashMap#isEmpty() just checks the same size variable which size() returns. It is mainly just a convenience method. One reason why you might want to use isEmpty() over manually comparing the size is that the former makes it clearer what your code is actually checking.