/* * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved. * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package sun.net.dns; import java.util.List; /** * The configuration of the client resolver. * * <p>A ResolverConfiguration is a singleton that represents the * configuration of the client resolver. The ResolverConfiguration * is opened by invoking the {@link #open() open} method. * * @since 1.4 */ public abstract class ResolverConfiguration {     private static final Object lock = new Object();     private static ResolverConfiguration provider;     protected ResolverConfiguration() { }     /**     * Opens the resolver configuration.     *     * @return the resolver configuration     */    public static ResolverConfiguration open() {        synchronized (lock) {            if (provider == null) {                provider = new sun.net.dns.ResolverConfigurationImpl();            }            return provider;        }    }     /**     * Returns a list corresponding to the domain search path. The     * list is ordered by the search order used for host name lookup.     * Each element in the list returns a {@link java.lang.String}     * containing a domain name or suffix.     *     * @return list of domain names     */    public abstract List<String> searchlist();     /**     * Returns a list of name servers used for host name lookup.     * Each element in the list returns a {@link java.lang.String}     * containing the textual representation of the IP address of     * the name server.     *     * @return list of the name servers     */    public abstract List<String> nameservers();      /**     * Options representing certain resolver variables of     * a {@link ResolverConfiguration}.     */    public static abstract class Options {         /**         * Returns the maximum number of attempts the resolver         * will connect to each name server before giving up         * and returning an error.         *         * @return the resolver attempts value or -1 is unknown         */        public int attempts() {            return -1;        }         /**         * Returns the basic retransmit timeout, in milliseconds,         * used by the resolver. The resolver will typically use         * an exponential backoff algorithm where the timeout is         * doubled for every retransmit attempt. The basic         * retransmit timeout, returned here, is the initial         * timeout for the exponential backoff algorithm.         *         * @return the basic retransmit timeout value or -1         *         if unknown         */        public int retrans() {            return -1;        }    }     /**     * Returns the {@link #Options} for the resolver.     *     * @return options for the resolver     */    public abstract Options options();}