public interface Weigher<K, V> {

  /**
   * Returns the weight of a cache entry. There is no unit for entry weights; rather they are simply
   * relative to each other.
   *
   * @return the weight of the entry; must be non-negative
   */
  int weigh(K key, V value);

  /** Returns a {@link Weigher} that returns the given {@code constant} for every request. */
  static Weigher<Object, Object> constantWeigher(int constant) {
    return new ConstantWeigher(constant);
  }

  /** Returns a {@link Weigher} that uses the integer key as the weight. */
  static Weigher<Integer, Object> intKeyWeigher() {
    return new IntKeyWeigher();
  }

    checkArgument(maximumSize >= 0, "maximum size must not be negative");
    this.maximumSize = maximumSize;
    return this;
  }

  /**
   * Specifies the maximum weight of entries the cache may contain. Weight is determined using the
   * {@link Weigher} specified with {@link #weigher}, and use of this method requires a

  }

  public void testEviction_weightedLru() {
    // test weighted lru within a single segment
    IdentityLoader<Integer> loader = identityLoader();
    LoadingCache<Integer, Integer> cache =
        CacheBuilder.newBuilder()
            .concurrencyLevel(1)
            .maximumWeight(45)
            .weigher(intKeyWeigher())
            .build(loader);
    CacheTesting.warmUp(cache, 0, 10);

    checkArgument(maximumSize >= 0, "maximum size must not be negative");
    this.maximumSize = maximumSize;
    return this;
  }

  /**
   * Specifies the maximum weight of entries the cache may contain. Weight is determined using the
   * {@link Weigher} specified with {@link #weigher}, and use of this method requires a

    assertWithMessage("removalListener")
        .that(actual.removalListener)
        .isEqualTo(expected.removalListener);
    assertWithMessage("weigher").that(actual.weigher).isEqualTo(expected.weigher);
    assertWithMessage("valueEquivalence")
        .that(actual.valueEquivalence)
        .isEqualTo(expected.valueEquivalence);

  public void testSetWeigher() {
    Weigher<Object, Object> testWeigher =
        new Weigher<Object, Object>() {
          @Override
          public int weigh(Object key, Object value) {
            return 42;
          }
        };
    LocalCache<Object, Object> map =
        makeLocalCache(createCacheBuilder().maximumWeight(1).weigher(testWeigher));
    assertThat(map.weigher).isSameInstanceAs(testWeigher);
  }

  public void testSetWeigher() {
    Weigher<Object, Object> testWeigher =
        new Weigher<Object, Object>() {
          @Override
          public int weigh(Object key, Object value) {
            return 42;
          }
        };
    LocalCache<Object, Object> map =
        makeLocalCache(createCacheBuilder().maximumWeight(1).weigher(testWeigher));
    assertThat(map.weigher).isSameInstanceAs(testWeigher);
  }

  }

  @GwtIncompatible // weigher
  public void testWeigher_withoutMaximumWeight() {
    CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder().weigher(constantWeigher(42));
    assertThrows(IllegalStateException.class, () -> builder.build(identityLoader()));
  }

  @GwtIncompatible // weigher
  public void testWeigher_withMaximumSize() {
    assertThrows(

      ValueReference<K, V> previous = entry.getValueReference();
      int weight = map.weigher.weigh(key, value);
      checkState(weight >= 0, "Weights must be non-negative");

      ValueReference<K, V> valueReference =
          map.valueStrength.referenceValue(this, entry, value, weight);
      entry.setValueReference(valueReference);
      recordWrite(entry, weight, now);
      previous.notifyNewValue(value);
    }