OnJava8-Examples/equalshashcode/SlowMap.java

// equalshashcode/SlowMap.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 Map implemented with ArrayLists
import java.util.*;
import onjava.*;

public class SlowMap<K, V> extends AbstractMap<K, V> {
  private List<K> keys = new ArrayList<>();
  private List<V> values = new ArrayList<>();
  @Override
  public V put(K key, V value) {
    V oldValue = get(key); // The old value or null
    if(!keys.contains(key)) {
      keys.add(key);
      values.add(value);
    } else
      values.set(keys.indexOf(key), value);
    return oldValue;
  }
  @Override
  public V get(Object key) { // key is type Object, not K
    if(!keys.contains(key))
      return null;
    return values.get(keys.indexOf(key));
  }
  @Override
  public Set<Map.Entry<K, V>> entrySet() {
    Set<Map.Entry<K, V>> set= new HashSet<>();
    Iterator<K> ki = keys.iterator();
    Iterator<V> vi = values.iterator();
    while(ki.hasNext())
      set.add(new MapEntry<>(ki.next(), vi.next()));
    return set;
  }
  public static void main(String[] args) {
    SlowMap<String,String> m= new SlowMap<>();
    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
*/