* 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) {

   * 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) {

  public void testExpiringMemoizedSupplierThreadSafe() throws Throwable {
    Function<Supplier<Boolean>, Supplier<Boolean>> memoizer =
        new Function<Supplier<Boolean>, Supplier<Boolean>>() {
          @Override
          public Supplier<Boolean> apply(Supplier<Boolean> supplier) {
            return Suppliers.memoizeWithExpiration(supplier, Long.MAX_VALUE, TimeUnit.NANOSECONDS);
          }
        };

  public void testExpiringMemoizedSupplierThreadSafe() throws Throwable {
    Function<Supplier<Boolean>, Supplier<Boolean>> memoizer =
        new Function<Supplier<Boolean>, Supplier<Boolean>>() {
          @Override
          public Supplier<Boolean> apply(Supplier<Boolean> supplier) {
            return Suppliers.memoizeWithExpiration(supplier, Long.MAX_VALUE, TimeUnit.NANOSECONDS);
          }
        };

        Striped.semaphore(256, 1));
  }

  private static final Supplier<ReadWriteLock> READ_WRITE_LOCK_SUPPLIER =
      new Supplier<ReadWriteLock>() {
        @Override
        public ReadWriteLock get() {
          return new ReentrantReadWriteLock();
        }
      };

  private static final Supplier<Lock> LOCK_SUPPLER =
      new Supplier<Lock>() {
        @Override
        public Lock get() {

        Striped.semaphore(256, 1));
  }

  private static final Supplier<ReadWriteLock> READ_WRITE_LOCK_SUPPLIER =
      new Supplier<ReadWriteLock>() {
        @Override
        public ReadWriteLock get() {
          return new ReentrantReadWriteLock();
        }
      };

  private static final Supplier<Lock> LOCK_SUPPLER =
      new Supplier<Lock>() {
        @Override
        public Lock get() {

import com.google.common.base.Supplier;
import java.util.concurrent.atomic.AtomicLong;

/**
 * Source of {@link LongAddable} objects that deals with GWT, Unsafe, and all that.
 *
 * @author Louis Wasserman
 */
@ElementTypesAreNonnullByDefault
final class LongAddables {
  private static final Supplier<LongAddable> SUPPLIER;

  static {
    Supplier<LongAddable> supplier;
    try {

      LongAdder unused = new LongAdder();
      supplier =
          new Supplier<LongAddable>() {
            @Override
            public LongAddable get() {
              return new LongAdder();
            }
          };
    } catch (Throwable t) { // we really want to catch *everything*
      supplier =
          new Supplier<LongAddable>() {
            @Override
            public LongAddable get() {