// equalshashcode/SimpleHashMap.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// A demonstration hashed Map
import java.util.*;
import onjava.*;

public
class SimpleHashMap<K, V> extends AbstractMap<K, V> {
 // Choose a prime number for the hash table
 // size, to achieve a uniform distribution:
 static final int SIZE = 997;
 // You can't have a physical array of generics,
 // but you can upcast to one:
 @SuppressWarnings("unchecked")
 LinkedList<MapEntry<K, V>>[] buckets =
 new LinkedList[SIZE];
 @Override
 public V put(K key, V value) {
 V oldValue = null;
 int index = Math.abs(key.hashCode()) % SIZE;
 if(buckets[index] == null)
 buckets[index] = new LinkedList<>();
 LinkedList<MapEntry<K, V>> bucket = buckets[index];
 MapEntry<K, V> pair = new MapEntry<>(key, value);
 boolean found = false;
 ListIterator<MapEntry<K, V>> it =
 bucket.listIterator();
 while(it.hasNext()) {
 MapEntry<K, V> iPair = it.next();
 if(iPair.getKey().equals(key)) {
 oldValue = iPair.getValue();
 it.set(pair); // Replace old with new
 found = true;
 break;
 }
 }
 if(!found)
 buckets[index].add(pair);
 return oldValue;
 }
 @Override
 public V get(Object key) {
 int index = Math.abs(key.hashCode()) % SIZE;
 if(buckets[index] == null) return null;
 for(MapEntry<K, V> iPair : buckets[index])
 if(iPair.getKey().equals(key))
 return iPair.getValue();
 return null;
 }
 @Override
 public Set<Map.Entry<K, V>> entrySet() {
 Set<Map.Entry<K, V>> set= new HashSet<>();
 for(LinkedList<MapEntry<K, V>> bucket : buckets) {
 if(bucket == null) continue;
 for(MapEntry<K, V> mpair : bucket)
 set.add(mpair);
 }
 return set;
 }
 public static void main(String[] args) {
 SimpleHashMap<String,String> m =
 new SimpleHashMap<>();
 m.putAll(Countries.capitals(8));
 m.forEach((k, v) ->
 System.out.println(k + "=" + v));
 System.out.println(m.get("BENIN"));
 m.entrySet().forEach(System.out::println);
 }
}
/* Output:
CAMEROON=Yaounde
ANGOLA=Luanda
BURKINA FASO=Ouagadougou
BURUNDI=Bujumbura
ALGERIA=Algiers
BENIN=Porto-Novo
CAPE VERDE=Praia
BOTSWANA=Gaberone
Porto-Novo
CAMEROON=Yaounde
ANGOLA=Luanda
BURKINA FASO=Ouagadougou
BURUNDI=Bujumbura
ALGERIA=Algiers
BENIN=Porto-Novo
CAPE VERDE=Praia
BOTSWANA=Gaberone
*/