first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data
centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be
configured to fall back for broad connectivity.

Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It
supports both synchronous blocking calls and async calls with callbacks.

By default, OkHttp will attempt a `MODERN_TLS` connection.  However by configuring the client connectionSpecs you can allow a fall back to `COMPATIBLE_TLS` connection if the modern configuration fails.

```java
OkHttpClient client = new OkHttpClient.Builder()
    .connectionSpecs(Arrays.asList(ConnectionSpec.MODERN_TLS, ConnectionSpec.COMPATIBLE_TLS))

    try {
      return Thread.class.getConstructor(
          ThreadGroup.class, Runnable.class, String.class, long.class, boolean.class);
    } catch (Throwable t) {
      // Probably pre Java 9. We'll fall back to Thread.inheritableThreadLocals.
      return null;
    }
  }

   *     the thread's interrupt status is set
   * @since 11.0
   */
  public Map<K, V> loadAll(Iterable<? extends K> keys) throws Exception {
    // This will be caught by getAll(), causing it to fall back to multiple calls to
    // LoadingCache.get
    throw new UnsupportedLoadingOperationException();
  }

  /**
   * Returns a cache loader that uses {@code function} to load keys, without supporting either

            update(3, charToThreeUtf8Bytes(c));
          } else {
            int codePoint = Character.codePointAt(input, i);
            if (codePoint == c) {
              // fall back to JDK getBytes instead of trying to handle invalid surrogates ourselves
              putBytes(input.subSequence(i, utf16Length).toString().getBytes(charset));
              return this;
            }
            i++;

      /*
       * https://github.com/google/guava/issues/6634: ProcessHandle has more accurate information,
       * but that class isn't available under all environments that we support. We use it if
       * available and fall back if not.
       */
      String fromSystemProperty = requireNonNull(USER_NAME.value());

      try {
        Class<?> processHandleClass = Class.forName("java.lang.ProcessHandle");

            update(3, charToThreeUtf8Bytes(c));
          } else {
            int codePoint = Character.codePointAt(input, i);
            if (codePoint == c) {
              // fall back to JDK getBytes instead of trying to handle invalid surrogates ourselves
              putBytes(input.subSequence(i, utf16Length).toString().getBytes(charset));
              return this;
            }
            i++;

  }

  /**
   * Provides a check of whether an exception type is valid for use with {@link
   * FuturesGetChecked#getChecked(Future, Class)}, possibly using caching.
   *
   * <p>Uses reflection to gracefully fall back to when certain implementations aren't available.
   */
  private static final class GetCheckedTypeValidatorHolder {
    static final GetCheckedTypeValidator BEST_VALIDATOR = getBestValidator();

            cells = rs;
            init = true;
          }
        } finally {
          busy = 0;
        }
        if (init) break;
      } else if (casBase(v = base, fn(v, x))) break; // Fall back on using base
    }
  }

  /** Sets base and all cells to the given value. */
  final void internalReset(long initialValue) {
    Cell[] as = cells;
    base = initialValue;
    if (as != null) {

  }

  /**
   * Ignored due to incompatibilities between Android and Java on how non-ASCII subject alt names
   * are parsed. Android fails to parse these, which means we fall back to the CN. The RI does parse
   * them, so the CN is unused.
   */
  @Test fun verifyNonAsciiSubjectAlt() {
    // Expecting actual:
    //  ["bar.com", "花子.co.jp"]