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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.mina.example.tennis;
21  
22  /**
23   * A tennis ball which has TTL value and state whose value is one of 'PING' and
24   * 'PONG'.
25   * 
26   * @author The Apache Directory Project (mina-dev@directory.apache.org)
27   * @version $Rev: 555855 $, $Date: 2007-07-13 05:19:00 +0200 (Fri, 13 Jul 2007) $
28   */
29  public class TennisBall {
30      private final boolean ping;
31  
32      private final int ttl;
33  
34      /**
35       * Creates a new ball with the specified TTL (Time To Live) value.
36       */
37      public TennisBall(int ttl) {
38          this(ttl, true);
39      }
40  
41      /**
42       * Creates a new ball with the specified TTL value and PING/PONG state.
43       */
44      private TennisBall(int ttl, boolean ping) {
45          this.ttl = ttl;
46          this.ping = ping;
47      }
48  
49      /**
50       * Returns the TTL value of this ball.
51       */
52      public int getTTL() {
53          return ttl;
54      }
55  
56      /**
57       * Returns the ball after {@link TennisPlayer}'s stroke.
58       * The returned ball has decreased TTL value and switched PING/PONG state.
59       */
60      public TennisBall stroke() {
61          return new TennisBall(ttl - 1, !ping);
62      }
63  
64      /**
65       * Returns string representation of this message (<code>[PING|PONG]
66       * (TTL)</code>).
67       */
68      public String toString() {
69          if (ping) {
70              return "PING (" + ttl + ")";
71          } else {
72              return "PONG (" + ttl + ")";
73          }
74      }
75  }