Is there BlockingMap as BlockingQueue in java?

Question

I'd like to have one BlockingMap data structure which is very similar to BlockingQueue. The take method of BlockingQueue will wait there until element is available. I'd like the get method of BlockingMap to wait there until the corresponding key is available? Is this kind of data structure available that I can use ?

Answer 1

I have simply used BlockingQueue<Map.Entry<K,V>> in the past. But recently, I came across this Blocking Map for Java. Haven't used it myself, though.

Answer 2

Here is an extremely simple implementation using BlockingQueue and ConcurrentHashMap:

public class BlockingMap<K, V> {     private Map<K, ArrayBlockingQueue<V>> map = new ConcurrentHashMap<>();      private BlockingQueue<V> getQueue(K key, boolean replace) {         return map.compute(key, (k, v) -> replace || v == null ? new ArrayBlockingQueue<>(1) : v);     }      public void put(K key, V value) {         getQueue(key, true).add(value);     }      public V get(K key) throws InterruptedException {         return getQueue(key, false).take();     }      public V get(K key, long timeout, TimeUnit unit) throws InterruptedException {         return getQueue(key, false).poll(timeout, unit);     } }