* factory classes like:
 *
 * <pre>
 * interface Book {...}
 * public class Books {
 *   public static Book hardcover(String title) {...}
 *   public static Book paperback(String title) {...}
 * }
 * </pre>
 *
 * <p>And all the created {@code Book} instances can be tested with:
 *
 * <pre>
 * new ClassSanityTester()

    // Warm up the client so the timing part of the test gets a pooled connection.
    server.enqueue(MockResponse())
    val warmUpCall =
      client.newCall(
        Request
          .Builder()
          .url(server.url("/"))
          .build(),
      )
    warmUpCall.execute().use { warmUpResponse -> warmUpResponse.body.string() }
    listener.clearAllEvents()

   * cast, for example:
   *
   * {@snippet :
   * Set<Object> aFewBadObjects = ...
   * Set<String> manyBadStrings = ...
   *
   * // impossible for a non-String to be in the intersection
   * SuppressWarnings("unchecked")
   * Set<String> badStrings = (Set) Sets.intersection(
   *     aFewBadObjects, manyBadStrings);
   * }
   *

 *       <a href="https://developer.android.com/studio/build/shrink-code">R8 and Proguard</a>.
 *   <li>It doesn't offer a way to wait for multiple events before taking action. For example, it
 *       doesn't offer a way to wait for multiple producers to all report that they're "ready," nor
 *       does it offer a way to batch multiple events from a single producer together.

    checkNotNull(mutex);
    this.delegate = delegate;
    this.mutex = mutex;
  }

  @Override
  protected Set<E> delegate() {
    return delegate;
  }

  @Override
  public String toString() {
    assertTrue(Thread.holdsLock(mutex));
    return super.toString();
  }

  @Override
  public boolean equals(@Nullable Object o) {
    assertTrue(Thread.holdsLock(mutex));

public static final String USE_WITNESS = "jcifs.smb.client.useWitness";
public static final String WITNESS_HEARTBEAT_TIMEOUT = "jcifs.smb.client.witnessHeartbeatTimeout";
public static final String WITNESS_REGISTRATION_TIMEOUT = "jcifs.smb.client.witnessRegistrationTimeout";
public static final String WITNESS_RECONNECT_DELAY = "jcifs.smb.client.witnessReconnectDelay";

        doAnswer(inv -> {
            // Simulate resolve call by setting names/types and thus enabling cache population
            Object[] args = inv.getArguments();
            String server = (String) args[0];
            CIFSContext c = (CIFSContext) args[1];
            assertNull(server); // We will pass null; method should forward it unchanged
            assertSame(ctx, c);

    checkNotNull(mutex);
    this.delegate = delegate;
    this.mutex = mutex;
  }

  @Override
  protected Set<E> delegate() {
    return delegate;
  }

  @Override
  public String toString() {
    assertTrue(Thread.holdsLock(mutex));
    return super.toString();
  }

  @Override
  public boolean equals(@Nullable Object o) {
    assertTrue(Thread.holdsLock(mutex));

    }

    /**
     * Record a write operation error
     */
    public void recordWriteError() {
        recordError();
    }

    @Override
    public String toString() {
        return String.format(
                "RdmaStatistics[reads=%d, writes=%d, sends=%d, receives=%d, "
                        + "bytes=%d, errors=%d, errorRate=%.3f, activeConnections=%d, activeMemRegions=%d]",

---------

This program downloads a URL and prints its contents as a string. [Full source][get_example].

```java
OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
  Request request = new Request.Builder()
      .url(url)
      .build();

  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}
```


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