Multiple indexes for a Java Collection - most basic solution?

Question

I\'m looking for the most basic solution to create multiple indexes on a Java Collection.

Required functionality:

• When a Value is removed, all index en

Answer 1

Google Collections LinkedListMultimap

About your first requirement

• When a Value is removed, all index entries associated with that value must be removed.

I think There is neither a library nor a Helper that supports it.

Here is how i have done by using LinkedListMultimap

Multimap multimap = LinkedListMultimap.create();

// Three duplicates entries
multimap.put(1, "A");
multimap.put(2, "B");
multimap.put(1, "A");
multimap.put(4, "C");
multimap.put(1, "A");

System.out.println(multimap.size()); // outputs 5

To get your first requirement, a Helper can play a good job

public static  void removeAllIndexEntriesAssociatedWith(Multimap multimap, V value) {
    Collection> eCollection = multimap.entries();
    for (Map.Entry entry : eCollection)
        if(entry.getValue().equals(value))
            eCollection.remove(entry);
}

...

removeAllIndexEntriesAssociatedWith(multimap, "A");

System.out.println(multimap.size()); // outputs 2

Google collections is

• lightweight
• Supported by Joshua Block (Effective Java)
• Nice features as ImmutableList, ImmutableMap and so on