使用值上的侦听器实现HashMap<K、ArrayList>，即ArrayList

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

public class HashMapWithListener<K, V> {
    private Map<K, List<V>> map;
    private ValueChangeListener<V> listener;

    public HashMapWithListener() {
        map = new HashMap<>();
    }

    public void put(K key, V value) {
        List<V> list = map.get(key);
        if (list == null) {
            list = new ArrayList<>();
            map.put(key, list);
        }
        list.add(value);
        if (listener != null) {
            listener.onValueChanged(key, list);
        }
    }

    public List<V> get(K key) {
        return map.get(key);
    }

    public void setValueChangeListener(ValueChangeListener<V> listener) {
        this.listener = listener;
    }

    public interface ValueChangeListener<V> {
        void onValueChanged(K key, List<V> value);
    }
}