public void close() throws IOException {
                super.close();
                counter[0]--;
              }
            };
          }
        };
    byte[] result = ByteSource.concat(checker, checker, checker).read();
    assertThat(result).hasLength(150);
  }

  private void joinHelper(Integer... spans) throws Exception {
    List<ByteSource> sources = new ArrayList<>();
    int start = 0;

              public void close() throws IOException {
                super.close();
                counter[0]--;
              }
            };
          }
        };
    byte[] result = ByteSource.concat(checker, checker, checker).read();
    assertThat(result).hasLength(150);
  }

  private void joinHelper(Integer... spans) throws Exception {
    List<ByteSource> sources = new ArrayList<>();
    int start = 0;

    }

    private void add(@Nullable Object[] elements, int n) {
      ensureRoomFor(n);
      /*
       * The following call is not statically checked, since arraycopy accepts plain Object for its
       * parameters. If it were statically checked, the checker would still be OK with it, since
       * we're copying into a `contents` array whose type allows it to contain nulls. Still, it's

### Exception Hierarchy

```
CrawlerSystemException (unchecked)  # Setup/config errors
CrawlingAccessException (checked)   # Runtime crawl errors
  ├─ MaxLengthExceededException
  └─ ChildUrlsException
ExtractException (checked)          # Extraction failures
  └─ UnsupportedExtractException
```

### Thread-Local Storage

```java
// Set (in CrawlerThread)

      } catch (Exception e) { // sneaky checked exception
        if (exception == null) {
          exception = e;
        } else {
          exception.addSuppressed(e);
        }
      }
    }
    if (exception != null) {
      // Normally this is a RuntimeException that doesn't need sneakyThrow.
      // But theoretically we could see sneaky checked exception
      sneakyThrow(exception);
    }
  }

      }

      @Override
      public void run() {
        try {
          delegate.run();
        } catch (Throwable t) {
          // Any Exception is either a RuntimeException or sneaky checked exception.

          /*
           * We fail this `ListenableFuture`, whose result is exposed to the user through the
           * `ListenableScheduledTask` we return from the `schedule*` methods.
           */

   */

  @Override
  public Object[] toArray() {
    return snapshotElementsToList().toArray();
  }

  @Override
  @SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
  public <T extends @Nullable Object> T[] toArray(T[] array) {
    return snapshotElementsToList().toArray(array);
  }

  /*

    GraphConnections<N, V> connectionsU = nodeConnections.get(nodeU);
    V value = (connectionsU == null) ? null : connectionsU.value(nodeV);
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.
    if (value == null) {
      return defaultValue;
    } else {
      return value;
    }
  }

       * prototype checker's JDK. However, the checker still sees the return type as plain
       * `Enumeration<?>`, probably because of one of the following two bugs (and maybe those two
       * bugs are themselves just symptoms of the same underlying problem):
       *
       * https://github.com/typetools/checker-framework/issues/3030
       *
       * https://github.com/typetools/checker-framework/issues/3236
       */

   * true when removing a connection from the pool; otherwise a racing caller might get it from the
   * pool when it shouldn't. Symmetrically, this must always be checked before returning a
   * connection from the pool.
   *
   * Once true this is always true. Guarded by this.
   */
  var noNewExchanges = false

  /**