*
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
@SuppressWarnings({
  // @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
  "JUnit4ClassUsedInJUnit3",
  // We use ::iterator so that we test passing a plain Iterable, not a Collection.
  "UnnecessaryMethodReference",
})

 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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,

 * sum that is used for purposes such as collecting statistics, not for fine-grained synchronization
 * control. Under low update contention, the two classes have similar characteristics. But under
 * high contention, expected throughput of this class is significantly higher, at the expense of
 * higher space consumption.
 *
 * <p>This class extends {@link Number}, but does not define methods such as {@code

	ErrIsFull = errors.New("ringbuffer is full")

	// ErrIsEmpty is returned when the buffer is empty and not blocking.
	ErrIsEmpty = errors.New("ringbuffer is empty")

	// ErrIsNotEmpty is returned when the buffer is not empty and not blocking.
	ErrIsNotEmpty = errors.New("ringbuffer is not empty")

	// ErrAcquireLock is returned when the lock is not acquired on Try operations.

   * infinite {@code double} values are considered infinitely far away. For example, 2^2000 is not
   * representable as a double, but {@code roundToDouble(BigDecimal.valueOf(2).pow(2000), HALF_UP)}
   * will return {@code Double.MAX_VALUE}, not {@code Double.POSITIVE_INFINITY}.
   *
   * <p>For the case of {@link RoundingMode#HALF_EVEN}, this implementation uses the IEEE 754

        assertThat(ClassLoaderUtil.isAncestor(cl3, cl1), is(true));
        assertThat(ClassLoaderUtil.isAncestor(cl2, cl1), is(true));

        assertThat(ClassLoaderUtil.isAncestor(cl1, cl2), is(not(true)));
        assertThat(ClassLoaderUtil.isAncestor(cl1, cl3), is(not(true)));
    }

public abstract class MessageDigestUtil {

    /**
     * Do not instantiate.
     */
    protected MessageDigestUtil() {
    }

    /**
     * Wraps the exception handling of {@link MessageDigest#getInstance(String)}.
     *
     * @param algorithm
     *            The algorithm (refer to the Javadoc of {@link MessageDigest} for available algorithms).
     *            Must not be {@literal null} or an empty string.

  private static final LazyLogger log = new LazyLogger(SequentialExecutor.class);

  enum WorkerRunningState {
    /** Runnable is not running and not queued for execution */
    IDLE,
    /** Runnable is not running, but is being queued for execution */
    QUEUING,
    /** runnable has been submitted but has not yet begun execution */
    QUEUED,
    RUNNING,
  }

  private static final LazyLogger log = new LazyLogger(SequentialExecutor.class);

  enum WorkerRunningState {
    /** Runnable is not running and not queued for execution */
    IDLE,
    /** Runnable is not running, but is being queued for execution */
    QUEUING,
    /** runnable has been submitted but has not yet begun execution */
    QUEUED,
    RUNNING,
  }

     *            null}.
     * @param session The repository session to use for resolving the plugin's main artifact, must not be {@code null}.
     * @return The resolved plugin artifact, never {@code null}.
     * @throws PluginResolutionException If the plugin artifact could not be resolved.
     */