* Optional.orElseGet}, except when {@code supplier} returns {@code null}. In this case this
   * method throws an exception, whereas the Java 8+ method returns the {@code null} to the caller.
   *
   * @throws NullPointerException if this optional's value is absent and the supplier returns {@code
   *     null}
   */
  public abstract T or(Supplier<? extends T> supplier);

  /**

 * which approach to use, <b>don't worry</b> too much about it; just pick something that seems
 * reasonable and it will be fine.
 *
 * <ul>
 *   <li>If checking whether the <i>caller</i> has violated your method or constructor's contract
 *       (such as by passing an invalid argument), use the utilities of the {@link Preconditions}
 *       class instead.

 *
 * <p>{@code ByteSource} provides two kinds of methods:
 *
 * <ul>
 *   <li><b>Methods that return a stream:</b> These methods should return a <i>new</i>, independent
 *       instance each time they are called. The caller is responsible for ensuring that the
 *       returned stream is closed.
 *   <li><b>Convenience methods:</b> These are implementations of common operations that are

      ImmutableList.of(0, 1, 2, 3, 4, 7, 10, 15, 20, 25, 40, 70);

  /* Helper function to make a Long value from an Integer. */
  private static final Function<Integer, Long> TO_LONG =
      new Function<Integer, Long>() {
        @Override
        public Long apply(Integer n) {
          return Long.valueOf(n);
        }
      };

  /* Helper function to make a BigInteger value from a Long. */

 *
 * <p>{@code CharSource} provides two kinds of methods:
 *
 * <ul>
 *   <li><b>Methods that return a reader:</b> These methods should return a <i>new</i>, independent
 *       instance each time they are called. The caller is responsible for ensuring that the
 *       returned reader is closed.
 *   <li><b>Convenience methods:</b> These are implementations of common operations that are

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import junit.framework.AssertionFailedError;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A helper for concurrency testing. One or more {@code TestThread} instances are instantiated in a
 * test with reference to the same "lock-like object", and then their interactions with that object

    return "z";
  }

  @Override
  protected String getValueNotInPopulatedMap() throws UnsupportedOperationException {
    return "26";
  }

  /** Helper assertion comparing two maps */
  private void assertMapsEqual(Map<?, ?> expected, Map<?, ?> map) {
    assertEquals(expected, map);
    assertEquals(expected.hashCode(), map.hashCode());

  }

  /**
   * Loads {@link WillBeUnloadedException} in a separate {@code ClassLoader}, calls {@code
   * getChecked(future, WillBeUnloadedException.class)}, and returns the loader. The caller can then
   * test that the {@code ClassLoader} can still be GCed. The test amounts to a test that {@code
   * getChecked} holds no strong references to the class.
   */

import java.util.SortedMap;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentSkipListMap;

/**
 * Helper classes for various benchmarks.
 *
 * @author Christopher Swenson
 */
final class BenchmarkHelpers {
  /** So far, this is the best way to test various implementations of {@link Set} subclasses. */

import java.util.SortedMap;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentSkipListMap;

/**
 * Helper classes for various benchmarks.
 *
 * @author Christopher Swenson
 */
final class BenchmarkHelpers {
  /** So far, this is the best way to test various implementations of {@link Set} subclasses. */