here's a very simple hash table implementation in java. in only implements put() and get(), but you can easily add whatever you like. it relies on java's hashCode() method that is implemented by all objects. you could easily create your own interface,
interface Hashable {
int getHash();
}
and force it to be implemented by the keys if you like.
public class Hashtable<K, V> {
private static class Entry<K,V> {
private final K key;
private final V val;
Entry(K key, V val) {
this.key = key;
this.val = val;
}
}
private static int BUCKET_COUNT = 13;
@SuppressWarnings("unchecked")
private List<Entry>[] buckets = new List[BUCKET_COUNT];
public Hashtable() {
for (int i = 0, l = buckets.length; i < l; i++) {
buckets[i] = new ArrayList<Entry<K,V>>();
}
}
public V get(K key) {
int b = key.hashCode() % BUCKET_COUNT;
List<Entry> entries = buckets[b];
for (Entry e: entries) {
if (e.key.equals(key)) {
return e.val;
}
}
return null;
}
public void put(K key, V val) {
int b = key.hashCode() % BUCKET_COUNT;
List<Entry> entries = buckets[b];
entries.add(new Entry<K,V>(key, val));
}
}