Key existence check in HashMap

Question

Is checking for key existence in HashMap always necessary?

I have a HashMap with say a 1000 entries and I am looking at improving the efficiency. If the HashMap is b

Answer 1

You won't gain anything by checking that the key exists. This is the code of HashMap:

@Override
public boolean containsKey(Object key) {
    Entry m = getEntry(key);
    return m != null;
}

@Override
public V get(Object key) {
    Entry m = getEntry(key);
    if (m != null) {
        return m.value;
    }
    return null;
}

Just check if the return value for get() is different from null.

This is the HashMap source code.

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Resources :

• HashMap source code Bad one
• HashMap source code Good one