*
   * @since 19.0
   */
  public Optional<Long> sizeIfKnown() {
    return Optional.absent();
  }

  /**
   * Returns the size of this source in bytes, even if doing so requires opening and traversing an
   * entire stream. To avoid a potentially expensive operation, see {@link #sizeIfKnown}.
   *
   * <p>The default implementation calls {@link #sizeIfKnown} and returns the value if present. If

    return this;
  }

  /**
   * Sets distinct values for {@code type}, so that when a class {@code Foo} is tested for {@link
   * Object#equals} and {@link Object#hashCode}, and its construction requires a parameter of {@code
   * type}, the distinct values of {@code type} can be passed as parameters to create {@code Foo}
   * instances that are unequal.
   *

```mermaid
flowchart LR
    stone(philosophers-stone) -->|requires| harry-1[harry v1]
```

Sonra daha ileri bir zamanda `prisoner-of-azkaban` adlı başka bir proje oluşturuyorsunuz; bu proje de `harry`'ye bağlı, fakat bu proje **`harry` versiyon `3`** istiyor.

```mermaid
flowchart LR
    azkaban(prisoner-of-azkaban) --> |requires| harry-3[harry v3]
```

    its purpose remains meaningful.

    (For example, a function in a library to compute square roots has
    a purpose that is entirely well-defined independent of the
    application.  Therefore, Subsection 2d requires that any
    application-supplied function or table used by this function must
    be optional: if the application does not supply it, the square
    root function must still compute square roots.)

@SuppressWarnings("module")
module okhttp3.urlconnection {
  requires okhttp3;

```mermaid
flowchart LR
    stone(philosophers-stone) -->|requires| harry-1[harry v1]
```

Затем вы создаёте другой проект `prisoner-of-azkaban`, который тоже зависит от `harry`, но ему нужен **`harry` версии `3`**.

```mermaid
flowchart LR
    azkaban(prisoner-of-azkaban) --> |requires| harry-3[harry v3]
```

@SuppressWarnings("module")
module okhttp3.java.net.cookiejar {
  requires okhttp3;
  exports okhttp3.java.net.cookiejar;

   * interface type.
   */
  // TODO: test other collections for this problem
  public void testOf_gwtArraycopyBug() {
    /*
     * The test requires:
     *
     * 1) An interface I extending Comparable<I> so that the created array is of
     * an interface type. 2) An instance of a class implementing that interface

  // We need to test that our method behaves like the JDK method.
  @SuppressWarnings("InlineMeInliner")
  public void testCompare() {
    for (long x : VALUES) {
      for (long y : VALUES) {
        // note: spec requires only that the sign is the same
        assertWithMessage("%s, %s", x, y).that(Longs.compare(x, y)).isEqualTo(Long.compare(x, y));
      }
    }
  }

  public void testContains() {

    }
}
```

### 7.2 Integration Tests
```java
@Test
@EnabledIfSystemProperty(named = "witness.test.enabled", matches = "true")
public void testWitnessFailover() throws Exception {
    // Requires cluster environment for testing
    CIFSContext context = getTestContext();
    context.getConfig().setProperty("jcifs.smb.client.useWitness", "true");