com.google.common.collect.Sets#newSetFromMap ( )源码实例Demo

@Override
public synchronized void initPipeline(ServletContext servletContext)
        throws ServletException {
    //double-checked lock, prevents duplicate initialization
    if (initialized)
        return;

    // Used to prevent duplicate initialization.
    Set<Filter> initializedSoFar = Sets.newSetFromMap(Maps.<Filter, Boolean>newIdentityHashMap());

    for (FilterDefinition filterDefinition : filterDefinitions) {
        filterDefinition.init(servletContext, objectGraph, initializedSoFar);
    }

    //next, initialize servlets...
    servletPipeline.init(servletContext, objectGraph);

    //everything was ok...
    initialized = true;
}
 

@Override
public void destroyPipeline() {
    //destroy servlets first
    servletPipeline.destroy();

    //go down chain and destroy all our filters
    Set<Filter> destroyedSoFar = Sets.newSetFromMap(Maps.<Filter, Boolean>newIdentityHashMap());
    for (FilterDefinition filterDefinition : filterDefinitions) {
        filterDefinition.destroy(destroyedSoFar);
    }
}
 

public void init(ServletContext servletContext, ObjectGraph objectGraph) throws ServletException {
    Set<HttpServlet> initializedSoFar
            = Sets.newSetFromMap(Maps.<HttpServlet, Boolean>newIdentityHashMap());

    for (ServletDefinition servletDefinition : servletDefinitions) {
        servletDefinition.init(servletContext, objectGraph, initializedSoFar);
    }
}
 

public void destroy() {
    Set<HttpServlet> destroyedSoFar
            = Sets.newSetFromMap(Maps.<HttpServlet, Boolean>newIdentityHashMap());
    for (ServletDefinition servletDefinition : servletDefinitions) {
        servletDefinition.destroy(destroyedSoFar);
    }
}
 

private <T> Set<T> createRelativeSet() {
    ConcurrentMap<T, Boolean> map = new MapMaker().weakKeys().makeMap();
    return Sets.newSetFromMap(map);
}
 

public static <V> Set<V> newConcurrentSet() {
    return Sets.newSetFromMap(ConcurrentCollections.<V, Boolean>newConcurrentMap());
}
 

public TypeSystemSmokeTester() throws NoSuchAlgorithmException {
	messageDigest = MessageDigest.getInstance("MD5");
	seen = Sets.newSetFromMap(new ConcurrentHashMap<BigInteger, Boolean>());
}
 

public DoSFilter() {
  numRecentAccesses = Maps.newConcurrentMap();
  bannedIPAddresses = Sets.newSetFromMap(Maps.<String,Boolean>newConcurrentMap());
}
 

/**
 * Creates a thread-safe set backed by a hash map. The set is backed by a
 * {@link ConcurrentHashMap} instance, and thus carries the same concurrency
 * guarantees.
 *
 * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be
 * used as an element. The set is serializable.
 *
 * @return a new, empty thread-safe {@code Set}
 * @since 15.0
 */
public static <E> Set<E> newConcurrentHashSet() {
  return Sets.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
}
 

/**
 * Creates a thread-safe set backed by a hash map. The set is backed by a
 * {@link ConcurrentHashMap} instance, and thus carries the same concurrency
 * guarantees.
 *
 * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be
 * used as an element. The set is serializable.
 *
 * @return a new, empty thread-safe {@code Set}
 * @since 15.0
 */
public static <E> Set<E> newConcurrentHashSet() {
  return Sets.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
}