<plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <executions>
          <execution>
            <id>default-compile</id>
            <configuration>
              <compilerArgs combine.children="append" combine.self="append">
                <arg>-XDignore.symbol.file</arg>
              </compilerArgs>
            </configuration>
          </execution>
          <execution>
            <id>compile-java9</id>

      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <executions>
          <execution>
            <id>default-compile</id>
            <configuration>
              <compilerArgs combine.children="append" combine.self="append">
                <arg>-XDignore.symbol.file</arg>
              </compilerArgs>
            </configuration>
          </execution>
          <execution>
            <id>compile-java9</id>

        <artifactId>maven-compiler-plugin</artifactId>
        <executions>
          <execution>
            <id>default-compile</id>
            <configuration>
              <compilerArgs combine.children="append" combine.self="append">
                <arg>-XDignore.symbol.file</arg>
              </compilerArgs>
            </configuration>
          </execution>
          <execution>
            <id>compile-java9</id>

   * input element is mapped to one cell in the returned table, with the rows, columns, and values
   * generated by applying the specified functions. If multiple inputs are mapped to the same row
   * and column pair, they will be combined with the specified merging function in encounter order.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time

          // There is no contract one way or another as long as isSubtypeOf() works as expected.
          combined.addAll(asList(typeParam.getBounds()));
          if (combined.size() > 1) { // Object is implicit and only useful if it's the only bound.
            combined.remove(Object.class);
          }
          return super.captureAsTypeVariable(combined.toArray(new Type[0]));
        }
      };
    }

   */
  private static final Collector<Object, ?, Optional<Object>> TO_OPTIONAL =
      Collector.of(
          ToOptionalState::new,
          ToOptionalState::add,
          ToOptionalState::combine,
          ToOptionalState::getOptional,
          Collector.Characteristics.UNORDERED);

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *

      }
    }

    @Override
    protected void processRemaining(ByteBuffer bb) {
      if (finished) {
        return;
      }
      crc0 = combine(0, crc0);
      crc0 = combine(crc0, crc1);
      crc0 = combine(crc0, crc2);
      crc0 = combine(crc0, crc3);
      while (bb.hasRemaining()) {
        crc0 = (crc0 >>> 8) ^ byteTable[(bb.get() ^ crc0) & 0xFF];
      }
      finished = true;
    }

    Throwable cause = e.getCause();
    if (cause == null) {
      throw e;
    }
    if (combineStackTraces) {
      StackTraceElement[] combined =
          ObjectArrays.concat(cause.getStackTrace(), e.getStackTrace(), StackTraceElement.class);
      cause.setStackTrace(combined);
    }
    if (cause instanceof Exception) {
      throw (Exception) cause;
    }
    if (cause instanceof Error) {

    byte[] murmur3Hash = Hashing.murmur3_32().hashLong(42L).asBytes();
    byte[] combined = new byte[md5Hash.length + murmur3Hash.length];
    ByteBuffer buffer = ByteBuffer.wrap(combined);
    buffer.put(md5Hash);
    buffer.put(murmur3Hash);
    HashCode expected = HashCode.fromBytes(combined);

    assertEquals(
        expected, Hashing.concatenating(Hashing.md5(), Hashing.murmur3_32()).hashLong(42L));

  public static <E extends @Nullable Object> FluentIterable<E> from(FluentIterable<E> iterable) {
    return checkNotNull(iterable);
  }

  /**
   * Returns a fluent iterable that combines two iterables. The returned iterable has an iterator
   * that traverses the elements in {@code a}, followed by the elements in {@code b}. The source
   * iterators are not polled until necessary.
   *