StopWatch


1   package jimm.util;
2   import java.io.PrintWriter  ;
3   
4   /**
5    * Prints time durations; used for development purposes only.
6    * <p>
7    * No threads or system resources are harmed in the making of a stop watch. A
8    * stop watch simply remembers the start time (and elapsed time when paused)
9    * and prints the total &quot;running&quot; time when either {@link #mark} or
10   * {@link #stop} is called.
11   * <p>
12   * {@link #stop} doesn't really stop anything. You can call stop as many times
13   * as you like and it will print the time elapsed since start. It would be
14   * easy to change this behavior, but I haven't needed to.
15   *
16   * @author Jim Menard, <a HREF="mailto:jimm@io.com">jimm@io.com</a>
17   */
18  public class StopWatch {
19  
20  protected String   name;
21  protected long t0;
22  protected long elapsedTime;
23  protected PrintWriter   out;
24  
25  public StopWatch() {
26      this(null, null);
27  }
28  
29  public StopWatch(String   name) {
30      this(name, null);
31  }
32  
33  public StopWatch(PrintWriter   out) {
34      this(null, out);
35  }
36  
37  public StopWatch(String   name, PrintWriter   out) {
38      this.name = name;
39      if (out == null)
40      this.out = new PrintWriter  (System.err);
41      else
42      this.out = out;
43      elapsedTime = -1L;      // So we can tell if we are ever started
44  }
45  
46  /**
47   * Remembers the current time and prints a message.
48   */
49  public void start() {
50      start(true);
51  }
52  
53  /**
54   * Remembers the current time and prints a message if requested.
55   *
56   * @param printStarting if <code>true</code> and this stop watch has a
57   * name, print a message
58   */
59  public void start(boolean printStarting) {
60      if (t0 != 0)
61      System.err.println("(warning: StopWatch already started; resetting)");
62      if (printStarting && name != null)
63      System.err.println("starting " + name);
64      elapsedTime = 0;
65      t0 = System.currentTimeMillis();
66  }
67  
68  /**
69   * Pauses the stop watch.
70   */
71  public void pause() {
72      long now = System.currentTimeMillis();
73      elapsedTime += now - t0;
74      t0 = 0;
75  }
76  
77  /**
78   * Resumes the stop watch.
79   */
80  public void resume() {
81      t0 = System.currentTimeMillis();
82  }
83  
84  /**
85   * Prints the current elapsed time without stopping.
86   */
87  public void mark() {
88      stop(null, true);
89  }
90  
91  /**
92   * Prints the current elapsed time without stopping, along with the
93   * stop watch name if <var>printMark</var> is <code>true</code>.
94   *
95   * @param printMark if <code>true</code>, the stop watch name will
96   * be printed
97   */
98  public void mark(boolean printMark) {
99      stop(null, printMark);
100 }
101 
102 /**
103  * Prints the current elapsed time without stopping, along with the
104  * stop watch name and <var>msg</var>.
105  *
106  * @param msg a message to print
107  */
108 public void mark(String   msg) {
109     stop(msg, true);
110 }
111 
112 /**
113  * Prints the current elapsed time without stopping, along with, along with
114  * the stop watch name if <var>printMark</var> is <code>true</code> and the
115  * <var>msg</var> if it's not <code>null</code>.
116  *
117  * @param msg a message to print
118  * @param printMark if <code>true</code>, the stop watch name will
119  * be printed
120  */
121 public void mark(String   msg, boolean printMark) {
122     stop(msg, printMark);
123 }
124 
125 /**
126  * Stops the stop watch and prints the name of this stop watch and the current
127  * elapsed time.
128  */
129 public void stop() {
130     stop(null, true);
131 }
132 
133 /**
134  * Stops the stop watch and prints the name of this stop watch,
135  * <var>msg</var> if non-<code>null</code>, and the current elapsed time.
136  *
137  * @param msg a message to print; may be <code>null</code>
138  */
139 public void stop(String   msg) {
140     stop(msg, true);
141 }
142 
143 /**
144  * Prints the current elapsed time, along with the stop watch name if
145  * <var>printMark</var> is <code>true</code> and the <var>msg</var> if it's
146  * not <code>null</code>.
147  *
148  * @param msg a message to print; may be <code>null</code>
149  * @param printName if <code>true</code>, the stop watch name will
150  * be printed
151  */
152 public void stop(String   msg, boolean printName) {
153     long now = System.currentTimeMillis();
154 
155     if (elapsedTime == -1) {
156     System.err.println("(StopWatch"
157                + (name != null ? (" \"" + name + '"') : "")
158                + " was stopped without ever being started)");
159     return;
160     }
161 
162     long total = elapsedTime;
163     if (t0 != 0)
164     total += now - t0;
165 
166     String   separator = null;
167     if (printName && name != null) {
168     System.err.print(name);
169     separator = ": ";
170     }
171     if (msg != null) {
172     if (separator != null)
173         System.err.print(' ');
174     System.err.print("(" + msg + ")");
175     separator = ": ";
176     }
177     if (separator != null)
178     System.err.print(separator);
179 
180     System.err.println("" + (total / 1000.0) + " seconds");
181 }
182 
183 }
184
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