*
         * Ideally we'd have a real eviction policy, but until we see a problem in practice, I hope
         * that this will suffice. I have not even benchmarked with different size limits.
         */
        if (validClasses.size() > 1000) {
          validClasses.clear();
        }

        validClasses.add(new WeakReference<Class<? extends Exception>>(exceptionClass));
      }
    }

    /**

    private static final Logger logger = LogManager.getLogger(PluginHelper.class);

    /**
     * Cache for storing available artifacts by type.
     * The cache expires after 5 minutes and has a maximum size of 10 entries.
     */
    protected LoadingCache<ArtifactType, Artifact[]> availableArtifacts = CacheBuilder.newBuilder()
            .maximumSize(10)
            .expireAfterWrite(5, TimeUnit.MINUTES)

 */
public class MD4 extends MessageDigest implements Cloneable {
    // MD4 specific object variables
    //...........................................................................

    /**
     * The size in bytes of the input block to the tranformation algorithm.
     */
    private static final int BLOCK_LENGTH = 64; //    = 512 / 8;

    /**
     * 4 32-bit words (interim result)
     */

              return indexOfEntryWithValue(left) - indexOfEntryWithValue(right);
            }

            int indexOfEntryWithValue(V value) {
              for (int i = 0; i < orderedEntries.size(); i++) {
                if (equal(orderedEntries.get(i).getValue(), value)) {
                  return i;
                }
              }
              throw new IllegalArgumentException(

        }

        if (_specification != null) {
            builder.setFetchSource(_specification.columnList.toArray(new String[_specification.columnList.size()]), null);
        }

        return builder;
    }

    // ===================================================================================

        }

        if (_specification != null) {
            builder.setFetchSource(_specification.columnList.toArray(new String[_specification.columnList.size()]), null);
        }

        return builder;
    }

    // ===================================================================================

        }

        result.add(sb.toString());

        // Validate
        if (quoteCount % 2 != 0) {
            return new String[0];
        }

        return result.toArray(new String[result.size()]);
    }

    private static String unQuoteUnEscape(final String original) {
        String result = original;

        // Unquote
        if (result.indexOf('\"') >= 0) {

          synchronized (result.lock) {
            assertEquals(
                "The test should have cleared the stack (say, by virtue of running runTearDown)",
                0,
                result.stack.size());
          }
        });
    return result;
  }

  private static final class ThrowingTearDown implements TearDown {

    private final String id;
    boolean ran = false;

    }
  }

  static char[] randomChars(Random rand, int size) {
    Set<Character> chars = new HashSet<>(size);
    for (int i = 0; i < size; i++) {
      char c;
      do {
        c = (char) rand.nextInt(Character.MAX_VALUE - Character.MIN_VALUE + 1);
      } while (chars.contains(c));
      chars.add(c);
    }
    char[] retValue = new char[chars.size()];
    int i = 0;
    for (char c : chars) {

    public boolean retainAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().retainAll(c);
      }
    }

    @Override
    public int size() {
      synchronized (mutex) {
        return delegate().size();
      }
    }

    @Override
    public @Nullable Object[] toArray() {
      synchronized (mutex) {
        return delegate().toArray();
      }
    }