Question

我想创建3个独立的现有Collection的Multimap实时视图。这样我只有一个中央集合来删除对象。

这应该是：

根据对象的属性，以类似池的方式简化对象的搜索。
提供一个中心位置，我可以从中删除对象。

Multimap<String,Products> searchProductsByCategory=null;
Multimap<String,Products> searchProductsByType=null;
Multimap<String,Products> searchProductsByPlaces=null;

Collection<Products> productsAvailable=getAvailableProducts();

//Create indexed Views of the products
searchProductsByCategory = Multimaps.index(productsAvailable, productsToCategoryFunction);
searchProductsByType = Multimaps.index(productsAvailable, productsToTypeFunction);
searchProductsByPlaces = Multimaps.index(productsAvailable, productsToPlacesFunction);

//Get Customers from database
Collection<Customer> customers=getCustomersFromDatabase();

List<Product> productsReserved=new LinkedList();
for(Customer customer:customers){

    Collection<String> categoriesChosen=getCustomerCategories(customer);

    for(String category:categoriesChosen){

        Collection<Product> tempResult=searchProductsByCategory.get(category);

        if (tempResult.isEmpty()){
            productsAvailable.removeAll(tempResult);
            productsReserved.addAll(tempResult);
        }
    }
}

//Here continuation of functionality based on Types and Places....

Answer 1

Multimaps.index()未返回视图，并且没有查看implementations。

你必须自己写一个get()只会过滤原始收藏。但是，它并不是非常有效，如果你不需要除get()以外的其他方法，你可能最好不要创建一个辅助函数。

public class LiveIndexMultimap<K, V> implements Multimap<K, V> {
    private final Collection<V> values;
    private final Function<? super V, K> keyFunction;

    public LiveIndexMultimap(Collection<V> values,
                             Function<? super V, K> keyFunction) {
        this.values = values;
        this.keyFunction = keyFunction;
    }

    public Collection<V> get(K key) {
        return FluentIterable.from(values)
                 .filter(Predicates.compose(Predicates.equalTo(key),
                         keyFunction)))
                 .toList(); // Copy needed if you want your example to work
    }

    // Other methods left as an exercice to the reader
}

如何使用Guava创建现有Collection的多个Multimap实时视图

1 个答案: