What is Hash Table?

A hash table is a data structure that is used to store key-value pairs in a way that allows for efficient lookup, insertion, and deletion operations. In this tutorial, we will show you how to implement a hash table in Java.

1. First, you will need to create a HashTable class that will hold the key-value pairs. The class should have an array of Linked Lists, where each linked list will represent a bucket.
2. Next, you will need to create a hash function that takes in a key and returns an index for the array of linked lists. A simple way to do this is to use the key’s hashCode and take the remainder when divided by the array size. This will ensure that the index is within the range of the array.

int hash(String key) {
    return key.hashCode() % array.length;
}

3. Now you can implement the put() method that takes in a key and a value and adds the key-value pair to the hash table. The method should first calculate the index using the hash function, then add the key-value pair to the appropriate linked list.

void put(String key, String value) {
    int index = hash(key);
    array[index].add(new Node(key, value));
}

4. Similarly, you can implement the get() method that takes in a key and returns the corresponding value. The method should first calculate the index using the hash function, then search the appropriate linked list for the key-value pair.

String get(String key) {
    int index = hash(key);
    for (Node node : array[index]) {
        if (node.key.equals(key)) {
            return node.value;
        }
    }
    return null;
}

5. Finally, you can implement the remove() method that takes in a key and removes the corresponding key-value pair from the hash table. The method should first calculate the index using the hash function, then search the appropriate linked list for the key-value pair and remove it.

void remove(String key) {
    int index = hash(key);
    for (Node node : array[index]) {
        if (node.key.equals(key)) {
            array[index].remove(node);
            break;
        }
    }
}

It is important to note that this is a basic implementation of the hash table and there are many variations and optimizations that can be made depending on the specific use case. Additionally, this example uses a very basic hash function, but in a real-world scenario, you would use a more robust hash function to minimize collisions.