doTestCollapseWithNoChange("");
    doTestCollapseWithNoChange("x");
    doTestCollapseWithNoChange("xx");
  }

  private void doTestCollapse(String in, String out) {
    // Try a few different matchers which all match '-' and not 'x'
    // Try replacement chars that both do and do not change the value.
    for (char replacement : new char[] {'_', '-'}) {
      String expected = out.replace('_', replacement);

    doTestCollapseWithNoChange("");
    doTestCollapseWithNoChange("x");
    doTestCollapseWithNoChange("xx");
  }

  private void doTestCollapse(String in, String out) {
    // Try a few different matchers which all match '-' and not 'x'
    // Try replacement chars that both do and do not change the value.
    for (char replacement : new char[] {'_', '-'}) {
      String expected = out.replace('_', replacement);

 * FutureTask}, {@code ListenableFutureTask} does not provide an overrideable {@link
 * FutureTask#done() done()} method. For similar functionality, call {@link #addListener}.
 *
 * <p>Few users should use this class. It is intended primarily for those who are implementing an
 * {@code ExecutorService}. Most users should call {@link ListeningExecutorService#submit(Callable)

    // It turns out that creating a new String is usually as fast, or faster
    // than wrapping cbuf in a light-weight CharSequence.
    target.append(new String(cbuf, off, len));
  }

  /*
   * Override a few functions for performance reasons to avoid creating unnecessary strings.
   */

  @Override
  public void write(int c) throws IOException {
    checkNotClosed();
    target.append((char) c);
  }

  @Override

 * FutureTask}, {@code ListenableFutureTask} does not provide an overrideable {@link
 * FutureTask#done() done()} method. For similar functionality, call {@link #addListener}.
 *
 * <p>Few users should use this class. It is intended primarily for those who are implementing an
 * {@code ExecutorService}. Most users should call {@link ListeningExecutorService#submit(Callable)

 *
 * <p>The classes in this package include:
 *
 * <h2>Immutable collections</h2>
 *
 * These are collections whose contents will never change. They also offer a few additional
 * guarantees (see {@link ImmutableCollection} for details). Implementations are available for both
 * the JDK collection types and the Guava collection types (listed below).
 *
 * <h2>Collection types</h2>
 *

 *
 * <p>The classes in this package include:
 *
 * <h2>Immutable collections</h2>
 *
 * These are collections whose contents will never change. They also offer a few additional
 * guarantees (see {@link ImmutableCollection} for details). Implementations are available for both
 * the JDK collection types and the Guava collection types (listed below).
 *
 * <h2>Collection types</h2>
 *

 *
 * <p>The simplest use case is:
 *
 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *
 * <p>This tests {@code foo.equals(foo)}, {@code foo.equals(null)}, and a few other operations.
 *
 * <p>For more extensive testing, add multiple equality groups. Each group should contain objects
 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>

 *
 * <p>The simplest use case is:
 *
 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *
 * <p>This tests {@code foo.equals(foo)}, {@code foo.equals(null)}, and a few other operations.
 *
 * <p>For more extensive testing, add multiple equality groups. Each group should contain objects
 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>

) : Lockable {
  private var nextQueueName = 10000
  private var coordinatorWaiting = false
  private var coordinatorWakeUpAt = 0L

  /**
   * When we need a new thread to run tasks, we call [Backend.execute]. A few microseconds later we
   * expect a newly-started thread to call [Runnable.run]. We shouldn't request new threads until
   * the already-requested ones are in service, otherwise we might create more threads than we need.
   *