}
  }

  public void testForSupplier() {
    Supplier<Integer> supplier = new CountingSupplier();
    Function<@Nullable Object, Integer> function = Functions.forSupplier(supplier);

    assertEquals(1, (int) function.apply(null));
    assertEquals(2, (int) function.apply("foo"));

    new EqualsTester()
        .addEqualityGroup(function, Functions.forSupplier(supplier))

   *
   * @throws NullPointerException if this optional's value is absent and the supplier returns {@code
   *     null}
   */
  public abstract T or(Supplier<? extends T> supplier);

  /**
   * Returns the contained instance if it is present; {@code null} otherwise. If the instance is
   * known to be present, use {@link #get()} instead.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's

    public <T extends FromTo<String, Integer> & Supplier<Long>> void checkArray(T f, String s) {
      calledWith(f, s);
    }

    void check() {
      runTester();
      FromTo<?, ?> defaultFunction = (FromTo<?, ?>) getDefaultParameterValue(0);
      assertEquals(0, defaultFunction.apply(null));
      Supplier<?> defaultSupplier = (Supplier<?>) defaultFunction;

          java.util.function.Supplier<M> multimapSupplier) {
    return CollectCollectors.<T, K, V, M>toMultimap(keyFunction, valueFunction, multimapSupplier);
  }

  /**
   * Returns a {@code Collector} accumulating entries into a {@code Multimap} generated from the
   * specified supplier. Each input element is mapped to a key and a stream of values, each of which

import java.util.EnumMap;
import java.util.EnumSet;
import java.util.LinkedHashMap;
import java.util.TreeMap;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.function.ToIntFunction;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import javax.annotation.CheckForNull;

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.io;

/**
 * Interface for a supplier of streams that can report whether a stream was opened and whether that
 * stream was closed. Intended for use in a test where only a single stream should be opened and
 * possibly closed.
 *
 * @author Colin Decker
 */

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Supplier;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.collect.Queues;
import com.google.common.util.concurrent.ForwardingListenableFuture.SimpleForwardingListenableFuture;

    SUPPORTS_REMOVE,
    CollectionFeature.SUPPORTS_ITERATOR_REMOVE,
    MultisetTestSuiteBuilder.NoRecurse.NO_ENTRY_SET, // Cannot create entries with count > 1
  };

  static final Supplier<TreeSet<String>> STRING_TREESET_FACTORY =
      new Supplier<TreeSet<String>>() {
        @Override
        public TreeSet<String> get() {
          return new TreeSet<>(Ordering.natural().nullsLast());
        }
      };

/**
 * A destination to which bytes can be written, such as a file. Unlike an {@link OutputStream}, a
 * {@code ByteSink} is not an open, stateful stream that can be written to and closed. Instead, it
 * is an immutable <i>supplier</i> of {@code OutputStream} instances.
 *
 * <p>{@code ByteSink} provides two kinds of methods:
 *
 * <ul>
 *   <li><b>Methods that return a stream:</b> These methods should return a <i>new</i>, independent

 */

package com.google.common.reflect;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.common.base.Predicate;
import com.google.common.base.Supplier;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;