* future version of {@code com.google.common.base.Supplier} will be made to <i>extend</i> {@code
 * java.util.function.Supplier}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Harry Heymann
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

/**
 * Legacy version of {@link java.util.function.Supplier java.util.function.Supplier}. Semantically,
 * this could be a factory, generator, builder, closure, or something else entirely. No guarantees
 * are implied by this interface.
 *
 * <p>The {@link Suppliers} class provides common suppliers and related utilities.
 *
 * <p>As this interface extends {@code java.util.function.Supplier}, an instance of this type can be

   * words, the new supplier's value will be computed by retrieving the value from {@code supplier},
   * and then applying {@code function} to that value. Note that the resulting supplier will not
   * call {@code supplier} or invoke {@code function} until it is called.
   */
  public static <F extends @Nullable Object, T extends @Nullable Object> Supplier<T> compose(
      Function<? super F, T> function, Supplier<F> supplier) {

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import java.security.Permission;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import junit.framework.TestCase;

  /**
   * Returns a cache loader based on an <i>existing</i> supplier instance. Note that there's no need
   * to create a <i>new</i> supplier just to pass it in here; just subclass {@code CacheLoader} and
   * implement {@link #load load} instead.
   *
   * <p>The returned object is serializable if {@code supplier} is serializable.
   *
   * @param supplier the supplier to be used for loading values; must never return {@code null}

  }

  private static void assertChecksum(ImmutableSupplier<Checksum> supplier, String input) {
    byte[] bytes = HashTestUtils.ascii(input);

    Checksum checksum = supplier.get();
    checksum.update(bytes, 0, bytes.length);
    long value = checksum.getValue();

    String toString = "name";
    HashFunction func = new ChecksumHashFunction(supplier, 32, toString);
    assertEquals(toString, func.toString());

  public void testOr_supplier_present() {
    assertEquals("a", Optional.of("a").or(Suppliers.ofInstance("fallback")));
  }

  public void testOr_supplier_absent() {
    assertEquals("fallback", Optional.absent().or(Suppliers.ofInstance("fallback")));
  }

  public void testOr_nullSupplier_absent() {
    Supplier<Object> nullSupplier = (Supplier<Object>) Suppliers.<@Nullable Object>ofInstance(null);

  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    return (Optional<T>) checkNotNull(secondChoice);
  }

  @Override
  public T or(Supplier<? extends T> supplier) {
    return checkNotNull(
        supplier.get(), "use Optional.orNull() instead of a Supplier that returns null");
  }

  @Override
  @CheckForNull
  public T orNull() {
    return null;
  }

  @Override
  public Set<T> asSet() {

  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    return (Optional<T>) checkNotNull(secondChoice);
  }

  @Override
  public T or(Supplier<? extends T> supplier) {
    return checkNotNull(
        supplier.get(), "use Optional.orNull() instead of a Supplier that returns null");
  }

  @Override
  @CheckForNull
  public T orNull() {
    return null;
  }

  @Override
  public Set<T> asSet() {

  }

  public static <E extends @Nullable Object> SpliteratorTester<E> of(
      Supplier<Spliterator<E>> spliteratorSupplier) {
    return new SpliteratorTester<>(
        ImmutableSet.of(() -> new GeneralSpliteratorOfObject<>(spliteratorSupplier.get())));
  }

  /**
   * @since 28.1
   */
  public static SpliteratorTester<Integer> ofInt(Supplier<Spliterator.OfInt> spliteratorSupplier) {
    return new SpliteratorTester<>(