Method containsValue

output/java_guava/1.4.17/LocalCache.java:4181–4219

(@Nullable Object value)

  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    // does not impact recency ordering
    if (value == null) {
      return false;
    }

    // This implementation is patterned after ConcurrentHashMap, but without the locking. The only
    // way for it to return a false negative would be for the target value to jump around in the map
    // such that none of the subsequent iterations observed it, despite the fact that at every point
    // in time it was present somewhere int the map. This becomes increasingly unlikely as
    // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible.

    long now = ticker.read();
    final Segment<K, V>[] segments = this.segments;
    long last = -1L;
    for (int i = 0; i < CONTAINS_VALUE_RETRIES; i++) {
      long sum = 0L;
      for (Segment<K, V> segment : segments) {
        // ensure visibility of most recent completed write
        int unused = segment.count; // read-volatile
        AtomicReferenceArray<ReferenceEntry<K, V>> table = segment.table;
        for (int j = 0; j < table.length(); j++) {
          for (ReferenceEntry<K, V> e = table.get(j); e != null; e = e.getNext()) {
            V v = segment.getLiveValue(e, now);
            if (v != null && valueEquivalence.equivalent(value, v)) {
              return true;
            }
          }
        }
        sum += segment.modCount;
      }
      if (sum == last) {
        break;
      }
      last = sum;
    }
    return false;
  }

  @Override
  public V put(K key, V value) {