StopWatch


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30  
31  
32  package org.hsqldb.lib;
33  
34  /**
35   * Provides the programatic analog of a physical stop watch. <p>
36   *
37   * The watch can be started, stopped and zeroed and can be queried for
38   * elapsed running time.  The watch accumulates elapsed time over starts
39   * and stops such that only the time actually spent running is recorded.
40   * If the watch is zeroed, then the accumulated time is discarded and
41   * the watch starts again with zero acumulated time. <p>
42   *
43   * @author boucherb@users
44   * @version 1.7.2
45   * @since 1.7.2
46   */
47  public class StopWatch {
48  
49      /**
50       * The last time this object made the transition
51       * from stopped to running state, as reported
52       * by System.currentTimeMillis().
53       */
54      private long startTime;
55      private long lastStart;
56  
57      /**
58       * The accumulated running time of this object since
59       * it was last zeroed.
60       */
61      private long total;
62  
63      /** Flags if this object is started or stopped. */
64      boolean running = false;
65  
66      /** Creates, zeros, and starts a new StopWatch */
67      public StopWatch() {
68          this(true);
69      }
70  
71      /** Creates, zeros, and starts a new StopWatch */
72      public StopWatch(boolean start) {
73  
74          if (start) {
75              start();
76          }
77      }
78  
79      /**
80       * Retrieves the accumulated time this object has spent running since
81       * it was last zeroed.
82       * @return the accumulated time this object has spent running since
83       * it was last zeroed.
84       */
85      public long elapsedTime() {
86  
87          if (running) {
88              return total + System.currentTimeMillis() - startTime;
89          } else {
90              return total;
91          }
92      }
93  
94      /**
95       * Retrieves the accumulated time this object has spent running since
96       * it was last started.
97       * @return the accumulated time this object has spent running since
98       * it was last started.
99       */
100     public long currentElapsedTime() {
101 
102         if (running) {
103             return System.currentTimeMillis() - startTime;
104         } else {
105             return 0;
106         }
107     }
108 
109     /** Zeros accumulated running time and restarts this object. */
110     public void zero() {
111 
112         total = 0;
113 
114         start();
115     }
116 
117     /**
118      * Ensures that this object is in the running state.  If this object is not
119      * running, then the call has the effect of setting the <code>startTime</code>
120      * attribute to the current value of System.currentTimeMillis() and setting
121      * the <code>running</code> attribute to <code>true</code>.
122      */
123     public void start() {
124         startTime = System.currentTimeMillis();
125         running   = true;
126     }
127 
128     /**
129      * Ensures that this object is in the stopped state.  If this object is
130      * in the running state, then this has the effect of adding to the
131      * <code>total</code> attribute the elapsed time since the last transition
132      * from stopped to running state and sets the <code>running</code> attribute
133      * to false. If this object is not in the running state, this call has no
134      * effect.
135      */
136     public void stop() {
137 
138         if (running) {
139             total   += System.currentTimeMillis() - startTime;
140             running = false;
141         }
142     }
143 
144     public void mark() {
145         stop();
146         start();
147     }
148 
149     /**
150      * Retrieves prefix + " in " + elapsedTime() + " ms."
151      * @param prefix The string to use as a prefix
152      * @return prefix + " in " + elapsedTime() + " ms."
153      */
154     public String   elapsedTimeToMessage(String   prefix) {
155         return prefix + " in " + elapsedTime() + " ms.";
156     }
157 
158     /**
159      * Retrieves prefix + " in " + elapsedTime() + " ms."
160      * @param prefix The string to use as a prefix
161      * @return prefix + " in " + elapsedTime() + " ms."
162      */
163     public String   currentElapsedTimeToMessage(String   prefix) {
164         return prefix + " in " + currentElapsedTime() + " ms.";
165     }
166 
167     /**
168      * Retrieves the internal state of this object, as a String.
169      *
170      * The retreived value is:
171      *
172      * <pre>
173      *    super.toString() +
174      *    "[running=" +
175      *    running +
176      *    ", startTime=" +
177      *    startTime +
178      *    ", total=" +
179      *    total + "]";
180      * </pre>
181      * @return the state of this object, as a String
182      */
183     public String   toString() {
184         return super.toString() + "[running=" + running + ", startTime="
185                + startTime + ", total=" + total + "]";
186     }
187 }
188
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