CODEWITHSUNDEEP
javahashmap
ambar
ambar

Reputation: 2253

Confusion over Java HashMap createEntry method

I'm trying to understand the inner implementation of HashMap in Java. I have a confusion with the 'createEntry' method. 

void createEntry(int hash, K key, V value, int bucketIndex) {
    Entry<K,V> e = table[bucketIndex];
    table[bucketIndex] = new Entry<>(hash, key, value, e);
    size++;
}

it creates an entry object 'e' and then it puts it to another entry object and stores it into the bucket[bucketindex] and it also stores the key and value. I am not able to understand the purpose of creation of the Entry object 'e' here. Could someone please explain.

Regards

Upvotes: 1

Views: 202

Answers (1)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279970

It gets the previous entry in the bucket (even if it is null). It then creates a new entry, setting its next entry to that previous one retrieved. It then sets the new entry to the same index in the bucket.

So say you had 3 element in hash

0: [null]
1: [some entry]
2: [null]

And you had to add to index 1

0: [null]
1: [new entry] -> [some entry]
2: [null]

Similarly, adding to index 0

0: [newer entry] -> [null]
1: [new entry] -> [some entry]
2: [null]

Upvotes: 6

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