Mechanism of Java HashMap

Reading Algorithms book, need to grasp the concept of a hashtable. They write about hashing with separate chaining and hashing with linear probing. I guess Java's HashMap is a hashtable, therefore I'm wondering what mechanism does HashMap use (chaining or probing)?

I need to implement simplest HashMap with get, put, remove. Could you point me at the good material to read that?

When the unique keys used for the Map are custom objects, we need to implement hashCode() function inside the corresponding type. Did I get it right or when is hashCode() needed?

HashMap stores key-value pair in Map.Entry (we all know)

HashMap works on hashing algorithm and uses hashCode() and equals() method in put() and get() methods. (even we know this)

When we call put method by passing key-value pair, HashMap uses Key **hashCode()** with hashing to **find out the index** to store the key-value pair. (this is important)

The Entry is **stored in the LinkedList**, so if there are already existing entry, it uses **equals() method to check if the passed key already exists** (even this is important)

if yes it overwrites the value else it creates a new entry and store this key-value Entry.

When we call get method by passing Key, again it uses the hashCode() to find the index in the array and then use equals() method to find the correct Entry and return it's value. (now this is obvious)