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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 <a href="http://mina.apache.org">Apache MINA Project</a>
27   */
28  public class TennisBall {
29      private final boolean ping;
30  
31      private final int ttl;
32  
33      /**
34       * Creates a new ball with the specified TTL (Time To Live) value.
35       */
36      public TennisBall(int ttl) {
37          this(ttl, true);
38      }
39  
40      /**
41       * Creates a new ball with the specified TTL value and PING/PONG state.
42       */
43      private TennisBall(int ttl, boolean ping) {
44          this.ttl = ttl;
45          this.ping = ping;
46      }
47  
48      /**
49       * Returns the TTL value of this ball.
50       */
51      public int getTTL() {
52          return ttl;
53      }
54  
55      /**
56       * Returns the ball after {@link TennisPlayer}'s stroke.
57       * The returned ball has decreased TTL value and switched PING/PONG state.
58       */
59      public TennisBall stroke() {
60          return new TennisBall(ttl - 1, !ping);
61      }
62  
63      /**
64       * Returns string representation of this message (<code>[PING|PONG]
65       * (TTL)</code>).
66       */
67      @Override
68      public String toString() {
69          if (ping) {
70              return "PING (" + ttl + ")";
71          } else {
72              return "PONG (" + ttl + ")";
73          }
74      }
75  }