* the type of the concrete implementation.
     */
    abstract S self();

    /** Drains the reference queues used by this segment, if any. */
    @GuardedBy("this")
    void maybeDrainReferenceQueues() {}

    /** Clears the reference queues used by this segment, if any. */
    void maybeClearReferenceQueues() {}

    /** Sets the value of the given {@code entry}. */

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to {@link Set} instances. Also see this class's counterparts
 * {@link Lists}, {@link Maps} and {@link Queues}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#sets">{@code Sets}</a>.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy

 *
 * <p><b>Note:</b> by default, the returned cache uses equality comparisons (the {@link
 * Object#equals equals} method) to determine equality for keys or values. However, if {@link
 * #weakKeys} was specified, the cache uses identity ({@code ==}) comparisons instead for keys.
 * Likewise, if {@link #weakValues} or {@link #softValues} was specified, the cache uses identity
 * comparisons for values.
 *