Example #1: MultiValueMap

package see613.core.datatypes;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * HashMap of key => list of values
 */
public class MultiValueMap<K, V> extends HashMap<K, List<V>> {
    private static final long serialVersionUID = 616L;

    private V defaultValue = null;


    public MultiValueMap(Map<? extends K, ? extends List<V>> m) {
        super(m);
    }

    public MultiValueMap(int initialCapacity, float loadFactor) {
        super(initialCapacity, loadFactor);
    }

    public MultiValueMap(int initialCapacity) {
        super(initialCapacity);
    }

    public MultiValueMap() {
        super();
    }

    public List<V> put(K key, V val) {
        return put(key, val, false);
    }

    public List<V> put(K key, V val, boolean withRepeats) {
        List<V> list;

        if ( !containsKey(key) ) {
            list = new ArrayList<V>();

            put(key, list);
        }
        else {
            list = get(key);
        }

        if ( withRepeats || !list.contains(val) ) {
            list.add(val);
        }
        return list;
    }

    public List<V> get(K key) {
        return ( containsKey(key) ) ? super.get(key) : new ArrayList<V>();
    }

    public V getOne(K key, int subIndex) {
        V value = defaultValue;

        if ( containsKey(key) ) {
            List<V> list = get(key);

            if ( list.size() > subIndex ) {
                value = list.get(subIndex);
            }
        }
        return value;
    }

    public V getOne(K key) {
        return getOne(key, 0);
    }

    public int sizeById(K key) {
        return get(key).size();
    }

    public V remove(K key, int subKey) {
        V value = null;

        if ( containsKey(key) ) {
            List<V> list = get(key);
            int subKeyIndex = list.indexOf(subKey);

            if ( subKeyIndex > -1 ) {
                value = list.remove(subKeyIndex);
            }

            if ( list.size() == 0 ) {
                remove(key);
            }
        }
        return value;
    }


}