guava/src/com/google/common/cache/LocalCache.java
@Nullable
  V getLiveValue(ReferenceEntry<K, V> entry, long now) {
    if (entry.getKey() == null) {
      return null;
    }
    V value = entry.getValueReference().get();
    if (value == null) {
      return null;
    }

    if (isExpired(entry, now)) {
      return null;
    }
    return value;
  }
@Nullable
  V getLiveValue(ReferenceEntry<K, V> entry, long now) {
    if (entry.getKey() == null) {
      return null;
    }
    V value = entry.getValueReference().get();
    if (value == null) {
      return null;
    }

    if (isExpired(entry, now)) {
      return null;
    }
    return value;
  }
Gets the value from an entry. Returns null if the entry is invalid, partially-collected,
loading, or expired. Unlike {@link Segment#getLiveValue} this method does not attempt to
cleanup stale entries. As such it should only be called outside of a segment context, such as
during iteration.