.put(BigInteger.class, BigInteger.ZERO)
          .put(BigDecimal.class, BigDecimal.ZERO)
          .put(CharSequence.class, "")
          .put(String.class, "")
          .put(Pattern.class, Pattern.compile(""))
          .put(MatchResult.class, createMatchResult())
          .put(TimeUnit.class, TimeUnit.SECONDS)
          .put(Charset.class, Charsets.UTF_8)

      // different from each other. If buildKeepingLast() collapsed duplicates, that might end up
      // not being true.
      Pattern pattern = Pattern.compile("Multiple entries with same key: four=(.*) and four=(.*)");
      assertThat(expected).hasMessageThat().matches(pattern);
      Matcher matcher = pattern.matcher(expected.getMessage());
      assertThat(matcher.matches()).isTrue();

   * for more important information about the Java 8+ transition.
   */
  public static Function<Object, String> toStringFunction() {
    return ToStringFunction.INSTANCE;
  }

  // enum singleton pattern
  private enum ToStringFunction implements Function<Object, String> {
    INSTANCE;

    @Override
    public String apply(Object o) {
      checkNotNull(o); // eager for GWT.
      return o.toString();
    }

    return Integer.toString(generateInt());
  }

  @Generates
  Comparable<?> generateComparable() {
    return generateString();
  }

  @Generates
  Pattern generatePattern() {
    return Pattern.compile(generateString());
  }

  @Generates
  Charset generateCharset() {
    return pickInstance(Charset.availableCharsets().values(), Charsets.UTF_8);
  }

  @Generates

    @ParametricNullness
    @SuppressWarnings("unchecked") // Cast from Supplier<Void> to Supplier<T> is always valid
    public T get() {
      // Because Supplier is read-heavy, we use the "double-checked locking" pattern.
      if (delegate != SUCCESSFULLY_COMPUTED) {
        synchronized (this) {
          if (delegate != SUCCESSFULLY_COMPUTED) {
            T t = delegate.get();
            value = t;

    checkNotNull(t);
    /*
     * TODO(cpovirk): Consider optimizing iterator() to catch IOOBE instead of doing bounds checks.
     *
     * TODO(cpovirk): Consider the UnsignedBytes pattern if it performs faster and doesn't cause
     * AOSP grief.
     */
    return new AbstractList<StackTraceElement>() {
      /*
       * The following requireNonNull calls are safe because we use jlaStackTrace() only if

    checkNotNull(t);
    /*
     * TODO(cpovirk): Consider optimizing iterator() to catch IOOBE instead of doing bounds checks.
     *
     * TODO(cpovirk): Consider the UnsignedBytes pattern if it performs faster and doesn't cause
     * AOSP grief.
     */
    return new AbstractList<StackTraceElement>() {
      /*
       * The following requireNonNull calls are safe because we use jlaStackTrace() only if

   * for more important information about the Java 8+ transition.
   */
  public static Function<Object, String> toStringFunction() {
    return ToStringFunction.INSTANCE;
  }

  // enum singleton pattern
  private enum ToStringFunction implements Function<Object, String> {
    INSTANCE;

    @Override
    public String apply(Object o) {
      checkNotNull(o); // eager for GWT.
      return o.toString();
    }

   *
   * The coding pattern above is heavily used in java.util, e.g. in ArrayList. There is a
   * RangeCheckMicroBenchmark in the JDK that was used to test this.
   *
   * But the methods in this class want to throw different exceptions, depending on the args, so it
   * appears that this pattern is not directly applicable. But we can use the ridiculous, devious

 * Running on Java 6, exceptions that cannot be thrown must be logged rather than being added to the
 * thrown exception as a suppressed exception.
 *
 * <p>This class is intended to be used in the following pattern:
 *
 * <pre>{@code
 * Closer closer = Closer.create();
 * try {
 *   InputStream in = closer.register(openInputStream());
 *   OutputStream out = closer.register(openOutputStream());
 *   // do stuff