*
 * <p>A call to any of the <i>enter</i> methods with <b>void</b> return type should always be
 * followed immediately by a <i>try/finally</i> block to ensure that the current thread leaves the
 * monitor cleanly:
 *
 * {@snippet :
 * monitor.enter();
 * try {
 *   // do things while occupying the monitor
 * } finally {
 *   monitor.leave();
 * }
 * }
 *

 * href="http://tools.ietf.org/html/rfc4648">RFC 4648</a>. For example, the expression:
 *
 * {@snippet :
 * BaseEncoding.base32().encode("foo".getBytes(US_ASCII))
 * }
 *
 * <p>returns the string {@code "MZXW6==="}, and
 *
 * {@snippet :
 * byte[] decoded = BaseEncoding.base32().decode("MZXW6===");
 * }
 *
 * <p>...returns the ASCII bytes of the string {@code "foo"}.
 *

 * annotated by {@link TestSubtype}.
 *
 * <p>These declaration methods rely on Java static type checking to make sure what we want to
 * assert as subtypes are really subtypes according to javac. For example:
 *
 * {@snippet :
 * class MySubtypeTests extends SubtypeTester {
 *   @TestSubtype(suppressGetSubtype = true, suppressGetSupertype = true)
 *   public <T> Iterable<? extends T> listIsSubtypeOfIterable(List<T> list) {

 * Tester to ensure forwarding wrapper works by delegating calls to the corresponding method with
 * the same parameters forwarded and return value forwarded back or exception propagated as is.
 *
 * <p>For example:
 *
 * {@snippet :
 * new ForwardingWrapperTester().testForwarding(Foo.class, new Function<Foo, Foo>() {
 *   public Foo apply(Foo foo) {
 *     return new ForwardingFoo(foo);
 *   }
 * });
 * }
 *
 * @author Ben Yu

 * {@link Map}) with a separator. It either appends the results to an {@link Appendable} or returns
 * them as a {@link String}. Example:
 *
 * {@snippet :
 * Joiner joiner = Joiner.on("; ").skipNulls();
 *  . . .
 * return joiner.join("Harry", null, "Ron", "Hermione");
 * }
 *
 * <p>This returns the string {@code "Harry; Ron; Hermione"}. Note that all input elements are

 * result. (If you want such access, you may prefer {@link Futures#addCallback
 * Futures.addCallback}.) Still, direct {@code addListener} calls are occasionally useful:
 *
 * {@snippet :
 * final String name = ...;
 * inFlight.add(name);
 * ListenableFuture<Result> future = service.query(name);
 * future.addListener(new Runnable() {
 *   public void run() {
 *     processedCount.incrementAndGet();

  }

  /**
   * A builder for creating {@link ImmutableValueGraph} instances, especially {@code static final}
   * graphs. Example:
   *
   * {@snippet :
   * static final ImmutableValueGraph<City, Distance> CITY_ROAD_DISTANCE_GRAPH =
   *     ValueGraphBuilder.undirected()
   *         .<City, Distance>immutable()
   *         .putEdgeValue(PARIS, BERLIN, kilometers(1060))

   *
   * {@snippet :
   * NavigableSet<E> set = synchronizedNavigableSet(new TreeSet<E>());
   *  ...
   * synchronized (set) {
   *   // Must be in the synchronized block
   *   Iterator<E> it = set.iterator();
   *   while (it.hasNext()) {
   *     foo(it.next());
   *   }
   * }
   * }
   *
   * <p>or:
   *
   * {@snippet :

   * not propagated (otherwise the original exception will be lost).
   *
   * <p>If {@code swallowIOException} is true then we never throw {@code IOException} but merely log
   * it.
   *
   * <p>Example:
   *
   * {@snippet :
   * public void useStreamNicely() throws IOException {
   *   SomeStream stream = new SomeStream("foo");
   *   boolean threw = true;
   *   try {
   *     // ... code which does something with the stream ...

 * its {@code close} method. You could use a finalizer to accomplish this, but that has a
 * number of well-known problems. Here is how you might use this class instead:
 *
 * {@snippet :
 * public class MyServer implements Closeable {
 *   private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();
 *   // You might also share this between several objects.
 *