HashMap.java

public 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();
      }
      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);
        System.out.println(buckets[i].display());
      }
    }
  
    public static class LinkedList {
      private Node first;
  
      public LinkedList() {
        first = null;
      }
  
      public void insert(int key) {
        if (isEmpty()) {
          first = new Node(key);
          return;
        }
  
        Node temp = findEnd(first);
        temp.setNext(new Node(key));
      }
  
      private Node findEnd(Node n) {
        if (n.getNext() == null) {
          return n;
        } else {
          return findEnd(n.getNext());
        }
      }
  
      public Node findKey(int key) {
        if (!isEmpty()) {
          return findKey(first, key);
        } else {
          System.out.println("List is empty");
          return null;
        }
      }
  
      private Node findKey(Node n, int key) {
        if (n.getKey() == key) {
          return n;
        } else if (n.getNext() == null) {
          System.out.println("Key not found");
          return null;
        } else {
          return findKey(n.getNext(), key);
        }
      }
  
      public void delete(int key) {
        if (!isEmpty()) {
          if (first.getKey() == key) {
            first = null;
          } else {
            delete(first, key);
          }
        } else {
          System.out.println("List is empty");
        }
      }
  
      private void delete(Node n, int key) {
        if (n.getNext().getKey() == key) {
          if (n.getNext().getNext() == null) {
            n.setNext(null);
          } else {
            n.setNext(n.getNext().getNext());
          }
        }
      }
  
      public String display() {
        return display(first);
      }
  
      private String display(Node n) {
        if (n == null) {
          return "null";
        } else {
          return n.getKey() + "->" + display(n.getNext());
        }
      }
  
      public boolean isEmpty() {
        return first == null;
      }
    }
  
    public static class Node {
      private Node next;
      private int key;
  
      public Node(int key) {
        next = null;
        this.key = key;
      }
  
      public Node getNext() {
        return next;
      }
  
      public int getKey() {
        return key;
      }
  
      public void setNext(Node next) {
        this.next = next;
      }
    }
  }