android/guava/src/com/google/common/util/concurrent/AtomicLongMap.java
public long get(K key) {
    AtomicLong atomic = map.get(key);
    return atomic == null ? 0L : atomic.get();
  }
public long get(K key) {
    AtomicLong atomic = map.get(key);
    return atomic == null ? 0L : atomic.get();
  }
Returns the value associated with {@code key}, or zero if there is no value associated with
{@code key}.