If you put the same key again then it will replace the old mapping because HashMap doesn’t allow duplicate keys. The same key will result in the same hashcode and will end up at the same position in the bucket.
Each bucket contains a linked list of Map.Entry object, which contains both Key and Value. Now Java will take the Key object from each entry and compare with this new key using equals() method, if that return true then value object in that entry will be replaced by new value.
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