CSCI-258-Labs/258/hashTableLab/Hashtable.java

public class Hashtable<T> {

    public static void main(String[] args) {
        Hashtable<String> ht = new Hashtable<String>();
        String s1 =
            "The divine rights of kings was a political " +
            "philosophy espoused by Chucky One back in the " +
            "day who lost his head on account of him being " +
            "a dumbass";
        String[] words = s1.split(" ");
        for (String s : words) ht.add(s);
        ht.printArray();

        int longestChain = ht.longestChain();

        int numberOfChains = ht.numberOfChains();

        // LINEAR PROBING :
        // Longest Chain : 4
        // Number of Chains : 3
        //
        // QUADRADIC PROBING :
        // Longest Chain : 4
        // Number of Chains : 2
        //
        // Less chains = quicker fetching

        System.out.println(
            "Longest Chain : " +
                longestChain +
                "\nNumber of Chains : " +
                numberOfChains
        );
    }

    private T[] table;
    private int size;
    private float loadFactor;

    public Hashtable() {
        this(11);
    }

    public Hashtable(int initialCapacity) {
        table = (T[]) new Object[initialCapacity];
        size = 0;
        loadFactor = 0.75f;
    }

    public void add(T elem) {
        if (size / (double) table.length > loadFactor) rehash();
        int i = Math.abs(elem.hashCode()) % table.length;

        int t = 0;
        while (table[i] != null) {
            // Linear Probing
            // i = (i + 1) % table.length;
            // Quadratic Probing
            i = (i + (t ^ 2)) % table.length;
            t++;
        }
        table[i] = elem;
        size++;
    }

    public boolean contains(T elem) {
        int i = Math.abs(elem.hashCode()) % table.length;
        int t = 0;
        while (table[i] != null && !table[i].equals(elem)) {
            // Linear Probing
            // i = (i + 1) % table.length;
            // Quadratic
            i = (i + (t ^ 2)) % table.length;
        }
        return table[i] != null;
    }

    public void printArray() {
        for (int i = 0; i < table.length; i++) System.out.println(
            i + ": " + table[i]
        );
    }

    public int longestChain() {
        int longest = 0;
        for (int i = 0; i < table.length; i++) {
            int j = i;

            while (i < table.length && table[i] != null) {
                i++;
            }

            int lengthOfChain = i - j;

            if (lengthOfChain > longest) longest = lengthOfChain;
        }

        return longest;
    }

    public int numberOfChains() {
        int threeOrMoreChains = 0;
        for (int i = 0; i < table.length; i++) {
            int j = i;
            while (i < table.length && table[i] != null) {
                i++;
            }

            int lengthOfChain = i - j;

            if (lengthOfChain > 3) threeOrMoreChains++;
        }

        return threeOrMoreChains;
    }

    public int size() {
        return size;
    }

    private void rehash() {
        T[] smallTable = table;
        table = (T[]) new Object[table.length * 2 + 1];
        for (int i = 0; i < smallTable.length; i++) if (
            smallTable[i] != null
        ) add(smallTable[i]);
    }
}