问题描述

我们现在有 BiMap 和 multiMap 的概念，但是有 multiBiMap 吗?所以我的意思是什么.在 multiMap 中，K 和 V 之间存在一对多关系，单个键可以关联到多个值，因此得名.在双地图中，您有 K，V 对，这是双向的，这意味着您也可以获得 V，K 关系.就像有两个常规地图但同步.我需要一个双向多图，您可以在其中结合这两个概念.

As we now, there is the concept of BiMap and multiMap but is there a multiBiMap ? so what do I mean by this. In multiMap you have one-to-many relationship between K and V, a single key can be associated to multiple value, hence the name. In bi map you have K,V pair which is bi-directional mean you can get V,K relationship as well. Like having a two regular maps but synchronized. I need a bi directional multi map where you combine these two concepts.

推荐答案

import java.util.Set;

import com.google.common.collect.HashMultimap;
import com.google.common.collect.SetMultimap;

public class ManyToMany<K, V> {
    private final SetMultimap<K, V> keysToValues = HashMultimap.create();

    private final SetMultimap<V, K> valuesToKeys = HashMultimap.create();

    public Set<V> getValues(K key) {
        return keysToValues.get(key);
    }

    public Set<K> getKeys(V value) {
        return valuesToKeys.get(value);
    }

    public boolean put(K key, V value) {
        return keysToValues.put(key, value) && valuesToKeys.put(value, key);
    }

    public boolean putAll(K key, Iterable<? extends V> values) {
        boolean changed = false;
        for (V value : values) {
            changed |= put(key, value);
        }
        return changed;
    }
}

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