[CC150v5] 8.10 Implement a Hashmap

Question

Design and implement a hash table which uses chaining (linked lists) to handle collisions.

Solution

I wrote this topic before (using Java source code as a reference). This time, I would like to take another (easier) approach.

The main part of this is to use an array of list structure like this:

LinkedList<Cell<K, V>>[] items;

And the Cell Class looks like this:

public class Cell<K, V> {
    private K key;
    private V value;

    public Cell(K k, V v) {
        key = k;
        value = v;
    }

    public boolean equivalent(Cell<K, V> c) {
        return equivalent(c.getKey());
    }

    public boolean equivalent(K k) {
        return key.equals(k);
    }

    public K getKey() {
        return key;
    }

    public V getValue() {
        return value;
    }
}

Code

written by me

public class HashMapCC150<K, V> {

    int size;
    LinkedList<Cell<K, V>>[] items;

    public HashMapCC150(int num) {
        this.size = num;
        items = (LinkedList<Cell<K, V>>[]) new LinkedList[10];
    }

    public V get(K k) {
        int hashValue = this.calculateHashCode(k);
        if (items[hashValue] == null) {
            items[hashValue] = new LinkedList<Cell<K, V>>();
            return null;
        }
        for (Cell<K, V> cell : items[hashValue]) {
            if (k.equals(cell.getKey())) {
                return cell.getValue();
            }
        }
        return null;
    }

    public V put(K k, V v) {
        int hashValue = this.calculateHashCode(k);
        if (items[hashValue] == null) {
            items[hashValue] = new LinkedList<Cell<K, V>>();
        }
        for (Cell<K, V> cell : items[hashValue]) {
            if (k.equals(cell.getKey())) {
                items[hashValue].remove(cell);
                break;
            }
        }
        Cell<K, V> newItem = new Cell<K, V>(k, v);
        items[hashValue].add(newItem);
        return null;
    }

    public V remove(K k) {
        // not written
        return null;
    }

    private int calculateHashCode(K k) {
        return k.toString().length() % size;
    }

    public static void main(String[] args) {
        HashMapCC150<String, String> map = new HashMapCC150<String, String>(10);
        map.put("kevin", "durant");
        map.put("steven", "curry");
        map.put("al", "jefferson");
        System.out.println(map.get("kevin"));
        System.out.println(map.get("steven"));
        System.out.println(map.get("al"));
        map.put("kevin", "martin");
        map.put("steven", "nash");
        map.put("kevin", "braynt");
        System.out.println(map.get("kevin"));
        System.out.println(map.get("steven"));
        System.out.println(map.get("al"));
    }
}

class Cell<K, V> {
    private K key;
    private V value;

    public Cell(K k, V v) {
        key = k;
        value = v;
    }

    public boolean equivalent(Cell<K, V> c) {
        return equivalent(c.getKey());
    }

    public boolean equivalent(K k) {
        return key.equals(k);
    }

    public K getKey() {
        return key;
    }

    public V getValue() {
        return value;
    }
}