Converter<String, Integer> converter = Maps.asConverter(biMap);
    assertNull(converter.convert(null));
    assertNull(converter.reverse().convert(null));
  }

  public void testAsConverter_isAView() throws Exception {
    BiMap<String, Integer> biMap = HashBiMap.create();
    biMap.put("one", 1);
    biMap.put("two", 2);
    Converter<String, Integer> converter = Maps.asConverter(biMap);

    Converter<String, Integer> converter = Maps.asConverter(biMap);
    assertNull(converter.convert(null));
    assertNull(converter.reverse().convert(null));
  }

  public void testAsConverter_isAView() throws Exception {
    BiMap<String, Integer> biMap = HashBiMap.create();
    biMap.put("one", 1);
    biMap.put("two", 2);
    Converter<String, Integer> converter = Maps.asConverter(biMap);

   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression a boolean expression
   * @param errorMessage the exception message to use if the check fails; will be converted to a
   *     string using {@link String#valueOf(Object)}
   * @throws IllegalArgumentException if {@code expression} is false
   */
  public static void checkArgument(boolean expression, @CheckForNull Object errorMessage) {

 * com.google.common.util.concurrent.ListenableFuture} can adapt between the two {@code Future}
 * types by using <a href="https://github.com/lukas-krecan/future-converter#java8-guava">{@code
 * net.javacrumbs.futureconverter.java8guava.FutureConverter}</a>.
 *
 * <h2>More on {@code CacheBuilder}</h2>
 *
 * {@code CacheBuilder} builds caches with any combination of the following features:

   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression a boolean expression
   * @param errorMessage the exception message to use if the check fails; will be converted to a
   *     string using {@link String#valueOf(Object)}
   * @throws IllegalArgumentException if {@code expression} is false
   */
  public static void checkArgument(boolean expression, @CheckForNull Object errorMessage) {