}
    }

    /**
     * Merges a frequency value from existing source with new value.
     */
    private static long mergeFrequency(final Map<String, Object> existingSource, final String fieldName, final long newValue) {
        final Object freqObj = existingSource.get(fieldName);
        if (freqObj == null) {
            return newValue;
        }

        V previousValue = oldValue.get();
        if (previousValue == null) {
          V newValue = loader.load(key);
          return set(newValue) ? futureValue : immediateFuture(newValue);
        }
        ListenableFuture<V> newValue = loader.reload(key, previousValue);
        if (newValue == null) {
          return immediateFuture(null);
        }

    // different value
    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(1, segment.count);
    assertThat(segment.get(key, hash)).isEqualTo(newValue);

    // cleared
    segment.setWeakValueReferenceForTesting(entry, oldValueRef);
    oldValueRef.clear();
    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(0, segment.count);

    // different value
    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(1, segment.count);
    assertThat(segment.get(key, hash)).isEqualTo(newValue);

    // cleared
    segment.setWeakValueReferenceForTesting(entry, oldValueRef);
    oldValueRef.clear();
    assertFalse(segment.replace(key, hash, oldValue, newValue));
    assertEquals(0, segment.count);

        Entry<Object, Object> entry = warmed.get(i - WARMUP_MIN);
        Object newValue = new Object();
        assertThat(cache.asMap().put(entry.getKey(), newValue)).isSameInstanceAs(entry.getValue());
        // don't let the new entry get GCed
        warmed.add(entryOf(entry.getKey(), newValue));
        Object newKey = new Object();
        assertThat(cache.asMap().put(newKey, entry.getValue())).isNull();

        V previousValue = oldValue.get();
        if (previousValue == null) {
          V newValue = loader.load(key);
          return set(newValue) ? futureValue : immediateFuture(newValue);
        }
        ListenableFuture<V> newValue = loader.reload(key, previousValue);
        if (newValue == null) {
          return immediateFuture(null);
        }

      long oldValue;
      long newValue;
      do {
        oldValue = data.get(longIndex);
        newValue = oldValue | mask;
        if (oldValue == newValue) {
          return false;
        }
      } while (!data.compareAndSet(longIndex, oldValue, newValue));

      // We turned the bit on, so increment bitCount.
      bitCount.increment();

    // different value
    assertThat(segment.replace(key, hash, oldValue, newValue)).isFalse();
    assertThat(segment.count).isEqualTo(1);
    assertThat(segment.get(key, hash)).isSameInstanceAs(newValue);

    // cleared
    entry.setValueReference(oldValueRef);
    assertThat(segment.get(key, hash)).isSameInstanceAs(oldValue);
    oldValueRef.clear();

    // different value
    assertThat(segment.replace(key, hash, oldValue, newValue)).isFalse();
    assertThat(segment.count).isEqualTo(1);
    assertThat(segment.get(key, hash)).isSameInstanceAs(newValue);

    // cleared
    entry.setValueReference(oldValueRef);
    assertThat(segment.get(key, hash)).isSameInstanceAs(oldValue);
    oldValueRef.clear();

        V value = localCache.get(key);
        if (value != null) {
          return value;
        }

        try {
          V newValue = valueLoader.call();
          // TODO(b/147136275): Perform a null check on the result.
          localCache.put(key, newValue);
          return newValue;
        } catch (Exception e) {
          throw new ExecutionException(e);
        }
      }
    }

    @Override