Just as a note, it is reasonable to make value “final” so that value can not be
nulled out between the test and its use.
Cheers,
— Jim
> On Jul 4, 2018, at 10:22 AM, Zheka Kozlov <orionllm...@gmail.com> wrote:
>
> Oh yes, you are right. Then this is not dead code, just a useless null
> check.
>
> 2018-07-04 19:55 GMT+07:00 Scott Palmer <swpal...@gmail.com>:
>
>> On Jul 4, 2018, at 5:42 AM, Zheka Kozlov <orionllm...@gmail.com> wrote:
>>>
>>> I noticed dead code in java.util.HashMap.merge():
>>>
>>> public V merge(K key, V value,
>>> BiFunction<? super V, ? super V, ? extends V>
>>> remappingFunction) {
>>> if (value == null)
>>> throw new NullPointerException();
>>>
>>> ...
>>>
>>> if (value != null) { *// Condition ' value != null' is always true*
>>> if (t != null)
>>> t.putTreeVal(this, tab, hash, key, value);
>>> else {
>>> tab[i] = newNode(hash, key, value, first);
>>> if (binCount >= TREEIFY_THRESHOLD - 1)
>>> treeifyBin(tab, hash);
>>> }
>>> ++modCount;
>>> ++size;
>>> afterNodeInsertion(true);
>>> }
>>> return value;
>>> }
>>>
>>> The code in the if branch will never be executed because `value` was
>>> previously checked at the beginning of the method.
>>>
>>> Is this a mistake?
>>
>> You mean it will ALWAYS be executed. Yes, it looks to me like the ‘if’ is
>> useless.
>>
>>
>>
