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   /*
    * Copyright 2015 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  
  package io.netty.resolver.dns;
  
  import io.netty.util.internal.PlatformDependent;
  
  import java.net.InetSocketAddress;
  import java.util.Collections;
  import java.util.List;
  
  final class ShuffledDnsServerAddressStream implements DnsServerAddressStream {
  
      private final List<InetSocketAddress> addresses;
      private int i;
  
      /**
       * Create a new instance.
       * @param addresses The addresses are not cloned. It is assumed the caller has cloned this array or otherwise will
       *                  not modify the contents.
       */
      ShuffledDnsServerAddressStream(List<InetSocketAddress> addresses) {
          this.addresses = addresses;
  
          shuffle();
      }
  
      private ShuffledDnsServerAddressStream(List<InetSocketAddress> addresses, int startIdx) {
          this.addresses = addresses;
          i = startIdx;
      }
  
      private void shuffle() {
          Collections.shuffle(addresses, PlatformDependent.threadLocalRandom());
      }
  
      @Override
      public InetSocketAddress next() {
          int i = this.i;
          InetSocketAddress next = addresses.get(i);
          if (++ i < addresses.size()) {
              this.i = i;
          } else {
              this.i = 0;
              shuffle();
          }
          return next;
      }
  
      @Override
      public int size() {
          return addresses.size();
      }
  
      @Override
      public ShuffledDnsServerAddressStream duplicate() {
          return new ShuffledDnsServerAddressStream(addresses, i);
      }
  
      @Override
      public String toString() {
          return SequentialDnsServerAddressStream.toString("shuffled", i, addresses);
      }
  }