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package java.security.cert;

import java.util.Collection;
import java.util.Collections;

/**
 * Parameters used as input for the Collection {@code CertStore}
 * algorithm.
 * <p>
 * This class is used to provide necessary configuration parameters
 * to implementations of the Collection {@code CertStore}
 * algorithm. The only parameter included in this class is the
 * {@code Collection} from which the {@code CertStore} will
 * retrieve certificates and CRLs.
 * <p>
 * <b>Concurrent Access</b>
 * <p>
 * Unless otherwise specified, the methods defined in this class are not
 * thread-safe. Multiple threads that need to access a single
 * object concurrently should synchronize amongst themselves and
 * provide the necessary locking. Multiple threads each manipulating
 * separate objects need not synchronize.
 *
 * @since       1.4
 * @author      Steve Hanna
 * @see         java.util.Collection
 * @see         CertStore
 */
public class CollectionCertStoreParameters
    implements CertStoreParameters {

    private final Collection<?> coll;

    /**
     * Creates an instance of {@code CollectionCertStoreParameters}
     * which will allow certificates and CRLs to be retrieved from the
     * specified {@code Collection}. If the specified
     * {@code Collection} contains an object that is not a
     * {@code Certificate} or {@code CRL}, that object will be
     * ignored by the Collection {@code CertStore}.
     * <p>
     * The {@code Collection} is <b>not</b> copied. Instead, a
     * reference is used. This allows the caller to subsequently add or
     * remove {@code Certificates} or {@code CRL}s from the
     * {@code Collection}, thus changing the set of
     * {@code Certificates} or {@code CRL}s available to the
     * Collection {@code CertStore}. The Collection {@code CertStore}
     * will not modify the contents of the {@code Collection}.
     * <p>
     * If the {@code Collection} will be modified by one thread while
     * another thread is calling a method of a Collection {@code CertStore}
     * that has been initialized with this {@code Collection}, the
     * {@code Collection} must have fail-fast iterators.
     *
     * @param collection a {@code Collection} of
     *        {@code Certificate}s and {@code CRL}s
     * @throws    NullPointerException if {@code collection} is
     * {@code null}
     */
    public CollectionCertStoreParameters(Collection<?> collection) {
        if (collection == null)
            throw new NullPointerException();
        coll = collection;
    }

    /**
     * Creates an instance of {@code CollectionCertStoreParameters} with
     * the default parameter values (an empty and immutable
     * {@code Collection}).
     */
    public CollectionCertStoreParameters() {
        coll = Collections.EMPTY_SET;
    }

    /**
     * Returns the {@code Collection} from which {@code Certificate}s
     * and {@code CRL}s are retrieved. This is <b>not</b> a copy of the
     * {@code Collection}, it is a reference. This allows the caller to
     * subsequently add or remove {@code Certificates} or
     * {@code CRL}s from the {@code Collection}.
     *
     * @return the {@code Collection} (never null)
     */
    public Collection<?> getCollection() {
        return coll;
    }

    /**
     * Returns a copy of this object. Note that only a reference to the
     * {@code Collection} is copied, and not the contents.
     *
     * @return the copy
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            /* Cannot happen */
            throw new InternalError(e.toString(), e);
        }
    }

    /**
     * Returns a formatted string describing the parameters.
     *
     * @return a formatted string describing the parameters
     */
    public String toString() {
        return "CollectionCertStoreParameters: [\n" +
                "  collection: " + coll + "\n" +
                "]";
    }
}
