HashMap

Node

package DataStructures.HashMap.Hashing;

class Node {
    int data;
    Node next;

    public Node(int data) {
        this.data = data;
        this.next = null;
    }
}

LinkedList

package DataStructures.HashMap.Hashing;

class LinkedList {

    private Node Head;
    private int size;

    public LinkedList() {
        Head = null;
        size = 0;
    }

    public void insert(int data) {

        Node temp = Head;
        Node newnode = new Node(data);
    
        size++;

        if(Head == null) {
            Head = newnode;
        }
        else {
            newnode.next = Head;
            Head = newnode;
        }
    }

    public void delete(int data) {
        if(size == 0) {
            System.out.println("UnderFlow!");
            return;
        }

        else {
            Node curr = Head;
            if (curr.data == data) {
                Head = curr.next;
                size--;
                return;
            }
            else {
                
                while(curr.next.next != null) {
                    if(curr.next.data == data){
                            curr.next = curr.next.next;
                            return;
                        }
                }

                System.out.println("Key not Found");
            }
        }
    }

    public void display() {
        Node temp = Head;
        while(temp != null) {
            System.out.printf("%d ",temp.data);
            temp = temp.next;
        }
        System.out.println();
    }
}

HashMap

package DataStructures.HashMap.Hashing;


class HashMap {
    private int hsize;
    private LinkedList[] buckets;

    public HashMap(int hsize) {
        buckets = new LinkedList[hsize];
        for (int i = 0; i < hsize; i++) {
            buckets[i] = new LinkedList();
            // Java requires explicit initialisaton of each object
        }
        this.hsize = hsize;
    }

    public int hashing(int key) {
        int hash = key % hsize;
        if (hash < 0)
            hash += hsize;
        return hash;
    }

    public void insertHash(int key) {
        int hash = hashing(key);
        buckets[hash].insert(key);
    }


    public void deleteHash(int key) {
        int hash = hashing(key);

        buckets[hash].delete(key);
    }

    public void displayHashtable() {
        for (int i = 0; i < hsize; i++) {
            System.out.printf("Bucket %d :", i);
            buckets[i].display();
        }
    }

}