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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.nio.channels;

import java.net.InetAddress;

import java.net.NetworkInterface;

import java.io.IOException;

/**

 * A token representing the membership of an Internet Protocol (IP) multicast

 * group.

 *

 * <p> A membership key may represent a membership to receive all datagrams sent

 * to the group, or it may be <em>source-specific</em>, meaning that it

 * represents a membership that receives only datagrams from a specific source

 * address. Whether or not a membership key is source-specific may be determined

 * by invoking its {@link #sourceAddress() sourceAddress} method.

 *

 * <p> A membership key is valid upon creation and remains valid until the

 * membership is dropped by invoking the {@link #drop() drop} method, or

 * the channel is closed. The validity of the membership key may be tested

 * by invoking its {@link #isValid() isValid} method.

 *

 * <p> Where a membership key is not source-specific and the underlying operation

 * system supports source filtering, then the {@link #block block} and {@link

 * #unblock unblock} methods can be used to block or unblock multicast datagrams

 * from particular source addresses.

 *

 * @see MulticastChannel

 *

 * @since 1.7

 */

public abstract class MembershipKey {

    /**

     * Initializes a new instance of this class.

     */

    protected MembershipKey() {

    }

    /**

     * Tells whether or not this membership is valid.

     *

     * <p> A multicast group membership is valid upon creation and remains

     * valid until the membership is dropped by invoking the {@link #drop() drop}

     * method, or the channel is closed.

     *

     * @return  {@code true} if this membership key is valid, {@code false}

     *          otherwise

     */

    public abstract boolean isValid();

    /**

     * Drop membership.

     *

     * <p> If the membership key represents a membership to receive all datagrams

     * then the membership is dropped and the channel will no longer receive any

     * datagrams sent to the group. If the membership key is source-specific

     * then the channel will no longer receive datagrams sent to the group from

     * that source address.

     *

     * <p> After membership is dropped it may still be possible to receive

     * datagrams sent to the group. This can arise when datagrams are waiting to

     * be received in the socket's receive buffer. After membership is dropped

     * then the channel may {@link MulticastChannel#join join} the group again

     * in which case a new membership key is returned.

     *

     * <p> Upon return, this membership object will be {@link #isValid() invalid}.

     * If the multicast group membership is already invalid then invoking this

     * method has no effect. Once a multicast group membership is invalid,

     * it remains invalid forever.

     */

    public abstract void drop();

    /**

     * Block multicast datagrams from the given source address.

     *

     * <p> If this membership key is not source-specific, and the underlying

     * operating system supports source filtering, then this method blocks

     * multicast datagrams from the given source address. If the given source

     * address is already blocked then this method has no effect.

     * After a source address is blocked it may still be possible to receive

     * be received in the socket's receive buffer.

     *

     * @param   source

     *          The source address to block

     *

     * @return  This membership key

     *

     * @throws  IllegalArgumentException

     *          If the {@code source} parameter is not a unicast address or

     *          is not the same address type as the multicast group

     * @throws  IllegalStateException

     *          If this membership key is source-specific or is no longer valid

     * @throws  UnsupportedOperationException

     *          If the underlying operating system does not support source

     *          filtering

     * @throws  IOException

     *          If an I/O error occurs

     */

    public abstract MembershipKey block(InetAddress source) throws IOException;

    /**

     * Unblock multicast datagrams from the given source address that was

     * previously blocked using the {@link #block(InetAddress) block} method.

     *

     * @param   source

     *          The source address to unblock

     *

     * @return  This membership key

     *

     * @throws  IllegalStateException

     *          If the given source address is not currently blocked or the

     *          membership key is no longer valid

     */

    public abstract MembershipKey unblock(InetAddress source);

    /**

     * Returns the channel for which this membership key was created. This

     * method will continue to return the channel even after the membership

     * becomes {@link #isValid invalid}.

     *

     * @return  the channel

     */

    public abstract MulticastChannel channel();

    /**

     * Returns the multicast group for which this membership key was created.

     * This method will continue to return the group even after the membership

     * becomes {@link #isValid invalid}.

     *

     * @return  the multicast group

     */

    public abstract InetAddress group();

    /**

     * Returns the network interface for which this membership key was created.

     * This method will continue to return the network interface even after the

     * membership becomes {@link #isValid invalid}.

     *

     * @return  the network interface

     */

    public abstract NetworkInterface networkInterface();

    /**

     * Returns the source address if this membership key is source-specific,

     * or {@code null} if this membership is not source-specific.

     *

     * @return  The source address if this membership key is source-specific,

     *          otherwise {@code null}

     */

    public abstract InetAddress sourceAddress();

}