/**
 * A simple, and vastly overly simplistic implementation of
 * a Hashtable.
 * SO simple that it does not even use generics!!!!
 * @author gtowell
 * Created: Feb 8, 2022
 */
public class SimpleHT {
    /**
     * A Non-generic key-value pair.
     * The key is always an integer and the value always a string
     */
    private class Pair {
        // the key.  Once set it cannot be changed
        public final Integer key;
        // the value
        public String value;

        //Create a key value pair.
        Pair(Integer ky, String val) {
            key = ky;
            value = val;
        }
    }
    //the array underlying this hashtable
    private Pair[] backingArray;
    
    /**
     * Initialize the array, and not much more
     */
    public SimpleHT() {
        // The backing array is of length 4.   This length is ties to the hashing function
        backingArray = new Pair[4];
    }

    /**
     * The hashing function.   Matched to the backing array length
     * @param k 
     * @return
     */
    private int h(int k) {
        return k % backingArray.length;
    }
    
    /**
     * Put a value into the hashtable.   No worries about collisions.
     * @param key the key 
     * @param value the value to be stored
     */
    public void put(Integer key, String value) {
        backingArray[h(key)] = new Pair(key, value);
    }

    /**
     * Get a value from the hashtable
     * @param key the key
     * @return the value associated with the key, or null is there is no
     * value
     */
    public String get(Integer key) {
        return backingArray[h(key)].value;
    }
    
    /**
     * Example of the use of SimpleHT
     * @param args   NOT USED
     */
    public static void main(String[] args) {
        SimpleHT sht = new SimpleHT();
        for (int i=0; i<10; i++) {
            System.out.println("adding item with key=" + i + " value=" + String.format("%c", 'a'+i));
            sht.put(i, String.format("%c", 'a'+i));
        }
        for (int i=0; i<10; i++)
            System.out.println("getting key="+i+"  value="+sht.get(i));
    }

}