Java Hash Tables and Hash Maps

1. But Hashtables store Key,Value pair. So how it is achieved?

Imagine a data structure like this:

Node<K, V>[] table;

public static class Node<K, V> {
    //voila! Key and Value stored here
    private K key;
    private V value;
    //make it a linked list
    private Node<K, V> next;

}

2. The key,value pair examples show "Telephone Directory" example, but they do not show how they are stored in Arrays or linked list. It is just Map.put(k,v) and Map.get(k). Linked list store "One Data" and "Pointer".. so how can we store both Keys and Values in Linked list( A picture might help in understanding)

Check point 1.

3. A bit more practical example for Hash Table than map.put("Rocket", 01111111111).

Here you go:

public class PersonIdentifier {
    private final int id;
    private final String ssn;

    public PersonIdentifier(int id, String ssn) {
        this.id = id;
        this.ssn = ssn;
    }
    //getters, NO setters since fields are final...

    //now the relevant methods!
    @Override
    public int hashCode() {
        //available since Java 7...
        return Objects.hash(id, ssn);
    }

    @Override
    public boolean equals(Object o) {
        if (o == null) return null;
        if (this == o) return true;
        if (!o.getClass().equals(this.getClass())) return false;
        Person another = (Person)o;
        return another.id == this.id && another.ssn.equals(this.ssn);
    }
}

//...

Map<PersonIdentifier, Person> peopleMap = new HashMap<>();
peopleMap.put(new PersonIdentifier(1, "123456789"), new Person(/* fill with values like firstName, lastName, etc... */));
peopleMap.put(new PersonIdentifier(2, "987654321"), new Person(/* fill with values like firstName, lastName, etc... */));
//and on...