*
 * <h2>More on {@code CacheBuilder}</h2>
 *
 * {@code CacheBuilder} builds caches with any combination of the following features:
 *
 * <ul>
 *   <li>automatic loading of entries into the cache
 *   <li>least-recently-used eviction when a maximum size is exceeded (note that the cache is
 *       divided into segments, each of which does LRU internally)
 *   <li>time-based expiration of entries, measured since last access or last write

 *
 * <h2>More on {@code CacheBuilder}</h2>
 *
 * {@code CacheBuilder} builds caches with any combination of the following features:
 *
 * <ul>
 *   <li>automatic loading of entries into the cache
 *   <li>least-recently-used eviction when a maximum size is exceeded (note that the cache is
 *       divided into segments, each of which does LRU internally)
 *   <li>time-based expiration of entries, measured since last access or last write

    cache.close()
    createNewCacheWithSize(10)
    set("a", "a", "a")
    set("b", "b", "b")
    set("c", "c", "c")
    set("d", "d", "d")
    set("e", "e", "e")
    cache["b"]!!.close() // 'B' is now least recently used.

    // Causing the size to grow to 12 should evict 'A'.
    set("f", "f", "f")
    // Causing the size to grow to 12 should evict 'C'.
    set("g", "g", "g")
    cache.flush()

   *
   * @param collection the collection whose complement should be stored in the enum set
   * @return a new, modifiable {@code EnumSet} containing all values of the enum that aren't present
   *     in the given collection
   * @throws IllegalArgumentException if {@code collection} is not an {@code EnumSet} instance and
   *     contains no elements
   */
  @J2ktIncompatible

   * and accesses that were performed on the map. The queue is drained on writes and when it exceeds
   * its capacity threshold.
   *
   * The Least Recently Used page replacement algorithm was chosen due to its simplicity, high hit
   * rate, and ability to be implemented with O(1) time complexity. The initial LRU implementation

 *  New: Don't fall back to common name (CN) verification for hostnames. This
    behavior was deprecated with RFC 2818 in May 2000 and was recently dropped
    from major web browsers.
 *  New: Honor the `Retry-After` response header. HTTP 503 (Unavailable)
    responses are retried automatically if this header is present and its delay
    is 0 seconds. HTTP 408 (Client Timeout) responses are retried automatically

    // Test and compile source roots.
    // ----------------------------------------------------------------------

    /**
     * Adds the given source if not already present.
     *
     * @param source the source to add
     *
     * @see #getSourceRoots()
     *
     * @since 4.0.0
     */
    public void addSourceRoot(SourceRoot source) {
        sources.add(source);

 * supports `http` and `https`. Use [java.net.URI][URI] for URLs with arbitrary schemes.
 *
 * ### Username and Password
 *
 * Username and password are either present, or the empty string `""` if absent. This class offers
 * no mechanism to differentiate empty from absent. Neither of these components are popular in

          checkEntryNotNull(keys[0], values[0]);
          for (int i = 1; i < size; i++) {
            // requireNonNull is safe because the first `size` elements have been filled in.
            Entry<K, V> prevEntry = requireNonNull(entryArray[i - 1]);
            Entry<K, V> entry = requireNonNull(entryArray[i]);
            K key = entry.getKey();
            V value = entry.getValue();
            checkEntryNotNull(key, value);

     * @param value the value to be associated with the specified key
     * @return the previous value associated with the specified key, or the specified value if the key was not present
     * @see ConcurrentHashMap#putIfAbsent(Object, Object)
     */
    public static <K, V> V putIfAbsent(final ConcurrentMap<K, V> map, final K key, final V value) {
        final V exists = map.putIfAbsent(key, value);