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Java example source code file (CacheBuilderFactory.java)

This example Java source code file (CacheBuilderFactory.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, cachebuilderfactory, durationspec, function, integer, iterable, list, nullable_to_optional, object, optional, optional_to_nullable, override, set, strength, threading, threads, timeunit, util

The CacheBuilderFactory.java Java example source code

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.cache;

import com.google.common.base.Function;
import com.google.common.base.MoreObjects;
import com.google.common.base.Objects;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.cache.LocalCache.Strength;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;

import java.util.List;
import java.util.Set;
import java.util.concurrent.TimeUnit;

import javax.annotation.Nullable;

/**
 * Helper class for creating {@link CacheBuilder} instances with all combinations of several sets of
 * parameters.
 *
 * @author mike nonemacher
 */
class CacheBuilderFactory {
  // Default values contain only 'null', which means don't call the CacheBuilder method (just give
  // the CacheBuilder default).
  private Set<Integer> concurrencyLevels = Sets.newHashSet((Integer) null);
  private Set<Integer> initialCapacities = Sets.newHashSet((Integer) null);
  private Set<Integer> maximumSizes = Sets.newHashSet((Integer) null);
  private Set<DurationSpec> expireAfterWrites = Sets.newHashSet((DurationSpec) null);
  private Set<DurationSpec> expireAfterAccesses = Sets.newHashSet((DurationSpec) null);
  private Set<DurationSpec> refreshes = Sets.newHashSet((DurationSpec) null);
  private Set<Strength> keyStrengths = Sets.newHashSet((Strength) null);
  private Set<Strength> valueStrengths = Sets.newHashSet((Strength) null);

  CacheBuilderFactory withConcurrencyLevels(Set<Integer> concurrencyLevels) {
    this.concurrencyLevels = Sets.newLinkedHashSet(concurrencyLevels);
    return this;
  }

  CacheBuilderFactory withInitialCapacities(Set<Integer> initialCapacities) {
    this.initialCapacities = Sets.newLinkedHashSet(initialCapacities);
    return this;
  }

  CacheBuilderFactory withMaximumSizes(Set<Integer> maximumSizes) {
    this.maximumSizes = Sets.newLinkedHashSet(maximumSizes);
    return this;
  }

  CacheBuilderFactory withExpireAfterWrites(Set<DurationSpec> durations) {
    this.expireAfterWrites = Sets.newLinkedHashSet(durations);
    return this;
  }

  CacheBuilderFactory withExpireAfterAccesses(Set<DurationSpec> durations) {
    this.expireAfterAccesses = Sets.newLinkedHashSet(durations);
    return this;
  }

  CacheBuilderFactory withRefreshes(Set<DurationSpec> durations) {
    this.refreshes = Sets.newLinkedHashSet(durations);
    return this;
  }

  CacheBuilderFactory withKeyStrengths(Set<Strength> keyStrengths) {
    this.keyStrengths = Sets.newLinkedHashSet(keyStrengths);
    Preconditions.checkArgument(!this.keyStrengths.contains(Strength.SOFT));
    return this;
  }

  CacheBuilderFactory withValueStrengths(Set<Strength> valueStrengths) {
    this.valueStrengths = Sets.newLinkedHashSet(valueStrengths);
    return this;
  }

  Iterable<CacheBuilder buildAllPermutations() {
    @SuppressWarnings("unchecked")
    Iterable<List combinations = buildCartesianProduct(concurrencyLevels,
        initialCapacities, maximumSizes, expireAfterWrites, expireAfterAccesses, refreshes,
        keyStrengths, valueStrengths);
    return Iterables.transform(combinations,
        new Function<List>() {
          @Override public CacheBuilder<Object, Object> apply(List combination) {
            return createCacheBuilder(
                (Integer) combination.get(0),
                (Integer) combination.get(1),
                (Integer) combination.get(2),
                (DurationSpec) combination.get(3),
                (DurationSpec) combination.get(4),
                (DurationSpec) combination.get(5),
                (Strength) combination.get(6),
                (Strength) combination.get(7));
          }
        });
  }

  private static final Function<Object, Optional NULLABLE_TO_OPTIONAL =
      new Function<Object, Optional() {
        @Override public Optional<?> apply(@Nullable Object obj) {
          return Optional.fromNullable(obj);
        }
      };

  private static final Function<Optional OPTIONAL_TO_NULLABLE =
      new Function<Optional() {
        @Override public Object apply(Optional<?> optional) {
          return optional.orNull();
        }
      };

  /**
   * Sets.cartesianProduct doesn't allow sets that contain null, but we want null to mean
   * "don't call the associated CacheBuilder method" - that is, get the default CacheBuilder
   * behavior. This method wraps the elements in the input sets (which may contain null) as
   * Optionals, calls Sets.cartesianProduct with those, then transforms the result to unwrap
   * the Optionals.
   */
  private Iterable<List buildCartesianProduct(Set... sets) {
    List<Set> optionalSets = Lists.newArrayListWithExpectedSize(sets.length);
    for (Set<?> set : sets) {
      Set<Optional optionalSet =
          Sets.newLinkedHashSet(Iterables.transform(set, NULLABLE_TO_OPTIONAL));
      optionalSets.add(optionalSet);
    }
    Set<List> cartesianProduct = Sets.cartesianProduct(optionalSets);
    return Iterables.transform(cartesianProduct,
        new Function<List, List>() {
          @Override public List<Object> apply(List> objs) {
            return Lists.transform(objs, OPTIONAL_TO_NULLABLE);
          }
        });
  }

  private CacheBuilder<Object, Object> createCacheBuilder(
      Integer concurrencyLevel, Integer initialCapacity, Integer maximumSize,
      DurationSpec expireAfterWrite, DurationSpec expireAfterAccess, DurationSpec refresh,
      Strength keyStrength, Strength valueStrength) {

    CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder();
    if (concurrencyLevel != null) {
      builder.concurrencyLevel(concurrencyLevel);
    }
    if (initialCapacity != null) {
      builder.initialCapacity(initialCapacity);
    }
    if (maximumSize != null) {
      builder.maximumSize(maximumSize);
    }
    if (expireAfterWrite != null) {
      builder.expireAfterWrite(expireAfterWrite.duration, expireAfterWrite.unit);
    }
    if (expireAfterAccess != null) {
      builder.expireAfterAccess(expireAfterAccess.duration, expireAfterAccess.unit);
    }
    if (refresh != null) {
      builder.refreshAfterWrite(refresh.duration, refresh.unit);
    }
    if (keyStrength != null) {
      builder.setKeyStrength(keyStrength);
    }
    if (valueStrength != null) {
      builder.setValueStrength(valueStrength);
    }
    return builder;
  }

  static class DurationSpec {
    private final long duration;
    private final TimeUnit unit;

    private DurationSpec(long duration, TimeUnit unit) {
      this.duration = duration;
      this.unit = unit;
    }

    public static DurationSpec of(long duration, TimeUnit unit) {
      return new DurationSpec(duration, unit);
    }

    @Override
    public int hashCode() {
      return Objects.hashCode(duration, unit);
    }

    @Override
    public boolean equals(Object o) {
      if (o instanceof DurationSpec) {
        DurationSpec that = (DurationSpec) o;
        return unit.toNanos(duration) == that.unit.toNanos(that.duration);
      }
      return false;
    }

    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("duration", duration)
          .add("unit", unit)
          .toString();
    }
  }
}




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