util/concurrent/TimeUnit.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package java.util.concurrent;

/**
 * A <tt>TimeUnit</tt> represents time durations at a given unit of
 * granularity and provides utility methods to convert across units,
 * and to perform timing and delay operations in these units.
 * <tt>TimeUnit</tt> is a &quot;featherweight&quot; class.
 * It does not maintain time information, but only helps organize and
 * use time representations that may be maintained separately across
 * various contexts.
 *
 * <p>This class cannot be directly instantiated.  Use the {@link
 * #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS}, and {@link
 * #NANOSECONDS} static instances that provide predefined units of
 * precision. If you use these frequently, consider statically
 * importing this class.
 *
 * <p>A <tt>TimeUnit</tt> is mainly used to inform blocking timeout
 * methods how the timeout parameter should be interpreted. For
 * example, the following code will timeout in 50 milliseconds if the
 * {@link java.util.concurrent.locks.Lock lock} is not available:
 *
 * <pre>  Lock lock = ...;
 *  if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
 * </pre>
 * while this code will timeout in 50 seconds:
 * <pre>
 *  Lock lock = ...;
 *  if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
 * </pre>
 *
 * Note however, that there is no guarantee that a particular timeout
 * implementation will be able to notice the passage of time at the
 * same granularity as the given <tt>TimeUnit</tt>.
 *
 * @since 1.5
 * @author Doug Lea
 */
public final class TimeUnit implements java.io.Serializable {
    /* ordered indices for each time unit */
    private static final int NS = 0;
    private static final int US = 1;
    private static final int MS = 2;
    private static final int S  = 3;

    /** quick lookup table for conversion factors */
    private static final int[] multipliers = { 1, 
                                       1000, 
                                       1000*1000, 
                                       1000*1000*1000 };

    /** lookup table to check saturation */
    private static final long[] overflows = { 
        // Note that because we are dividing these down anyway, 
        // we don't have to deal with asymmetry of MIN/MAX values.
        0, // unused
        Long.MAX_VALUE / 1000,
        Long.MAX_VALUE / (1000 * 1000),
        Long.MAX_VALUE / (1000 * 1000 * 1000) };

    /** the index of this unit */
    private int index;
    /** Common name for unit */
    private final String unitName;

    /** private constructor */
    TimeUnit(int index, String name) { 
        this.index = index; 
        this.unitName = name;
    }

    /** Unit for one-second granularities. */
    public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
    /** Unit for one-millisecond granularities. */
    public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
    /** Unit for one-microsecond granularities. */
    public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
    /** Unit for one-nanosecond granularities. */
    public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");

    /**
     * Utility method to compute the excess-nanosecond argument to
     * wait, sleep, join.
     */
    private int excessNanos(long time, long ms) {
        if (index == NS)
            return (int) (time  - (ms * multipliers[MS-NS]));
        else if (index == US)
            return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
        else
            return 0;
    }

    /**
     * Perform conversion based on given delta representing the
     * difference between units
     * @param delta the difference in index values of source and target units
     * @param duration the duration
     * @return converted duration or saturated value
     */
    private static long doConvert(int delta, long duration) {
        if (delta == 0)
            return duration;
        if (delta < 0) 
            return duration / multipliers[-delta];
        if (duration > overflows[delta])
            return Long.MAX_VALUE;
        if (duration < -overflows[delta])
            return Long.MIN_VALUE;
        return duration * multipliers[delta];
    }

    /**
     * Convert the given time duration in the given unit to this
     * unit.  Conversions from finer to coarser granularities
     * truncate, so lose precision. For example converting
     * <tt>999</tt> milliseconds to seconds results in
     * <tt>0</tt>. Conversions from coarser to finer granularities
     * with arguments that would numerically overflow saturate to
     * <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
     * if positive.
     *
     * @param duration the time duration in the given <tt>unit</tt>
     * @param unit the unit of the <tt>duration</tt> argument
     * @return the converted duration in this unit,
     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively
     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
     */
    public long convert(long duration, TimeUnit unit) {
        return doConvert(unit.index - index, duration);
    }

    /**
     * Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
     * @param duration the duration
     * @return the converted duration,
     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively
     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
     * @see #convert
     */
    public long toNanos(long duration) {
        return doConvert(index, duration);
    }

    /**
     * Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
     * @param duration the duration
     * @return the converted duration,
     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively
     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
     * @see #convert
     */
    public long toMicros(long duration) {
        return doConvert(index - US, duration);
    }

    /**
     * Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
     * @param duration the duration
     * @return the converted duration,
     * or <tt>Long.MIN_VALUE</tt> if conversion would negatively
     * overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
     * @see #convert
     */
    public long toMillis(long duration) {
        return doConvert(index - MS, duration);
    }

    /**
     * Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
     * @param duration the duration
     * @return the converted duration.
     * @see #convert
     */
    public long toSeconds(long duration) {
        return doConvert(index - S, duration);
    }

    /**
     * Perform a timed <tt>Object.wait</tt> using this time unit.
     * This is a convenience method that converts timeout arguments
     * into the form required by the <tt>Object.wait</tt> method.
     *
     * <p>For example, you could implement a blocking <tt>poll</tt>
     * method (see {@link BlockingQueue#poll BlockingQueue.poll}
     * using:
     *
     * <pre>  public synchronized  Object poll(long timeout, TimeUnit unit) throws InterruptedException {
     *    while (empty) {
     *      unit.timedWait(this, timeout);
     *      ...
     *    }
     *  }</pre>
     *
     * @param obj the object to wait on
     * @param timeout the maximum time to wait. 
     * @throws InterruptedException if interrupted while waiting.
     * @see Object#wait(long, int)
     */
    public void timedWait(Object obj, long timeout)
        throws InterruptedException {
        if (timeout > 0) {
            long ms = toMillis(timeout);
            int ns = excessNanos(timeout, ms);
            obj.wait(ms, ns);
        }
    }

    /**
     * Perform a timed <tt>Thread.join</tt> using this time unit.
     * This is a convenience method that converts time arguments into the
     * form required by the <tt>Thread.join</tt> method.
     * @param thread the thread to wait for
     * @param timeout the maximum time to wait
     * @throws InterruptedException if interrupted while waiting.
     * @see Thread#join(long, int)
     */
    public void timedJoin(Thread thread, long timeout)
        throws InterruptedException {
        if (timeout > 0) {
            long ms = toMillis(timeout);
            int ns = excessNanos(timeout, ms);
            thread.join(ms, ns);
        }
    }

    /**
     * Perform a <tt>Thread.sleep</tt> using this unit.
     * This is a convenience method that converts time arguments into the
     * form required by the <tt>Thread.sleep</tt> method.
     * @param timeout the minimum time to sleep
     * @throws InterruptedException if interrupted while sleeping.
     * @see Thread#sleep
     */
    public void sleep(long timeout) throws InterruptedException {
        if (timeout > 0) {
            long ms = toMillis(timeout);
            int ns = excessNanos(timeout, ms);
            Thread.sleep(ms, ns);
        }
    }

    /**
     * Return the common name for this unit.
     */
    public String toString() {
        return unitName;
    }

    /**
     * Resolves instances being deserialized to a single instance per
     * unit.
     */
    private Object readResolve() {
        switch(index) {
        case NS: return NANOSECONDS;
        case US: return MICROSECONDS;
        case MS: return MILLISECONDS;
        case  S: return SECONDS;
        default: assert(false); return null;
        }
    }
}
Revision:	1.19
Committed:	Sun Jan 11 23:19:55 2004 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.18:	+13 -8 lines
Log Message:	formatting; grammar
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.18	* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5	dl	1.2	*/
6
7	tim	1.1	package java.util.concurrent;
8
9			/**
10	tim	1.6	* A <tt>TimeUnit</tt> represents time durations at a given unit of
11			* granularity and provides utility methods to convert across units,
12			* and to perform timing and delay operations in these units.
13			* <tt>TimeUnit</tt> is a "featherweight" class.
14			* It does not maintain time information, but only helps organize and
15			* use time representations that may be maintained separately across
16	tim	1.1	* various contexts.
17			*
18	dl	1.12	* <p>This class cannot be directly instantiated. Use the {@link
19			* #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS}, and {@link
20			* #NANOSECONDS} static instances that provide predefined units of
21			* precision. If you use these frequently, consider statically
22			* importing this class.
23	tim	1.1	*
24	dl	1.19	* <p>A <tt>TimeUnit</tt> is mainly used to inform blocking timeout
25			* methods how the timeout parameter should be interpreted. For
26			* example, the following code will timeout in 50 milliseconds if the
27			* {@link java.util.concurrent.locks.Lock lock} is not available:
28			*
29	tim	1.1	* <pre> Lock lock = ...;
30			* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
31			* </pre>
32			* while this code will timeout in 50 seconds:
33	tim	1.6	* <pre>
34	tim	1.1	* Lock lock = ...;
35			* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
36			* </pre>
37	dl	1.15	*
38			* Note however, that there is no guarantee that a particular timeout
39			* implementation will be able to notice the passage of time at the
40			* same granularity as the given <tt>TimeUnit</tt>.
41	tim	1.1	*
42			* @since 1.5
43	dl	1.4	* @author Doug Lea
44	tim	1.1	*/
45			public final class TimeUnit implements java.io.Serializable {
46	dl	1.14	/* ordered indices for each time unit */
47			private static final int NS = 0;
48			private static final int US = 1;
49			private static final int MS = 2;
50			private static final int S = 3;
51
52			/** quick lookup table for conversion factors */
53			private static final int[] multipliers = { 1,
54			1000,
55			1000*1000,
56			100010001000 };
57
58			/** lookup table to check saturation */
59			private static final long[] overflows = {
60			// Note that because we are dividing these down anyway,
61			// we don't have to deal with asymmetry of MIN/MAX values.
62			0, // unused
63			Long.MAX_VALUE / 1000,
64			Long.MAX_VALUE / (1000 * 1000),
65			Long.MAX_VALUE / (1000 * 1000 * 1000) };
66
67			/** the index of this unit */
68			private int index;
69			/** Common name for unit */
70			private final String unitName;
71
72			/** private constructor */
73			TimeUnit(int index, String name) {
74			this.index = index;
75			this.unitName = name;
76			}
77
78			/** Unit for one-second granularities. */
79			public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
80			/** Unit for one-millisecond granularities. */
81			public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
82			/** Unit for one-microsecond granularities. */
83			public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
84			/** Unit for one-nanosecond granularities. */
85			public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
86
87			/**
88			* Utility method to compute the excess-nanosecond argument to
89	dl	1.15	* wait, sleep, join.
90	dl	1.14	*/
91			private int excessNanos(long time, long ms) {
92			if (index == NS)
93			return (int) (time - (ms * multipliers[MS-NS]));
94			else if (index == US)
95			return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
96			else
97			return 0;
98			}
99	tim	1.1
100			/**
101	dl	1.14	* Perform conversion based on given delta representing the
102	dl	1.13	* difference between units
103			* @param delta the difference in index values of source and target units
104			* @param duration the duration
105			* @return converted duration or saturated value
106			*/
107			private static long doConvert(int delta, long duration) {
108			if (delta == 0)
109			return duration;
110			if (delta < 0)
111			return duration / multipliers[-delta];
112			if (duration > overflows[delta])
113			return Long.MAX_VALUE;
114			if (duration < -overflows[delta])
115			return Long.MIN_VALUE;
116			return duration * multipliers[delta];
117			}
118
119			/**
120	dl	1.17	* Convert the given time duration in the given unit to this
121			* unit. Conversions from finer to coarser granularities
122	dl	1.13	* truncate, so lose precision. For example converting
123			* <tt>999</tt> milliseconds to seconds results in
124			* <tt>0</tt>. Conversions from coarser to finer granularities
125			* with arguments that would numerically overflow saturate to
126			* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
127			* if positive.
128	tim	1.1	*
129			* @param duration the time duration in the given <tt>unit</tt>
130			* @param unit the unit of the <tt>duration</tt> argument
131	dl	1.17	* @return the converted duration in this unit,
132	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
133	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
134	tim	1.1	*/
135			public long convert(long duration, TimeUnit unit) {
136	dl	1.13	return doConvert(unit.index - index, duration);
137	dl	1.2	}
138
139			/**
140	dl	1.12	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
141	dl	1.2	* @param duration the duration
142	dl	1.13	* @return the converted duration,
143	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
144	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
145	dl	1.13	* @see #convert
146			*/
147	dl	1.2	public long toNanos(long duration) {
148	dl	1.13	return doConvert(index, duration);
149			}
150
151			/**
152			* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
153			* @param duration the duration
154			* @return the converted duration,
155			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
156			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
157			* @see #convert
158			*/
159			public long toMicros(long duration) {
160			return doConvert(index - US, duration);
161			}
162
163			/**
164			* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
165			* @param duration the duration
166			* @return the converted duration,
167			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
168			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
169			* @see #convert
170			*/
171			public long toMillis(long duration) {
172			return doConvert(index - MS, duration);
173			}
174
175			/**
176			* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
177			* @param duration the duration
178			* @return the converted duration.
179			* @see #convert
180			*/
181			public long toSeconds(long duration) {
182			return doConvert(index - S, duration);
183	tim	1.1	}
184	tim	1.6
185	tim	1.1	/**
186	dl	1.17	* Perform a timed <tt>Object.wait</tt> using this time unit.
187	dl	1.19	* This is a convenience method that converts timeout arguments
188			* into the form required by the <tt>Object.wait</tt> method.
189			*
190			* <p>For example, you could implement a blocking <tt>poll</tt>
191			* method (see {@link BlockingQueue#poll BlockingQueue.poll}
192			* using:
193			*
194	tim	1.1	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
195			* while (empty) {
196			* unit.timedWait(this, timeout);
197			* ...
198			* }
199			* }</pre>
200	dl	1.19	*
201	tim	1.1	* @param obj the object to wait on
202	dl	1.10	* @param timeout the maximum time to wait.
203	tim	1.1	* @throws InterruptedException if interrupted while waiting.
204			* @see Object#wait(long, int)
205			*/
206			public void timedWait(Object obj, long timeout)
207			throws InterruptedException {
208	dl	1.10	if (timeout > 0) {
209	dl	1.15	long ms = toMillis(timeout);
210	dl	1.10	int ns = excessNanos(timeout, ms);
211			obj.wait(ms, ns);
212			}
213	tim	1.1	}
214
215			/**
216	dl	1.17	* Perform a timed <tt>Thread.join</tt> using this time unit.
217	tim	1.1	* This is a convenience method that converts time arguments into the
218			* form required by the <tt>Thread.join</tt> method.
219			* @param thread the thread to wait for
220			* @param timeout the maximum time to wait
221			* @throws InterruptedException if interrupted while waiting.
222			* @see Thread#join(long, int)
223			*/
224			public void timedJoin(Thread thread, long timeout)
225			throws InterruptedException {
226	dl	1.10	if (timeout > 0) {
227	dl	1.15	long ms = toMillis(timeout);
228	dl	1.10	int ns = excessNanos(timeout, ms);
229			thread.join(ms, ns);
230			}
231	tim	1.1	}
232	tim	1.6
233	tim	1.1	/**
234	dl	1.17	* Perform a <tt>Thread.sleep</tt> using this unit.
235	tim	1.1	* This is a convenience method that converts time arguments into the
236			* form required by the <tt>Thread.sleep</tt> method.
237	tim	1.6	* @param timeout the minimum time to sleep
238	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
239			* @see Thread#sleep
240			*/
241			public void sleep(long timeout) throws InterruptedException {
242	dl	1.10	if (timeout > 0) {
243	dl	1.15	long ms = toMillis(timeout);
244	dl	1.10	int ns = excessNanos(timeout, ms);
245			Thread.sleep(ms, ns);
246			}
247	tim	1.1	}
248
249	dl	1.9	/**
250			* Return the common name for this unit.
251			*/
252			public String toString() {
253			return unitName;
254	dl	1.13	}
255
256			/**
257	dl	1.14	* Resolves instances being deserialized to a single instance per
258			* unit.
259	dl	1.13	*/
260	dl	1.14	private Object readResolve() {
261			switch(index) {
262			case NS: return NANOSECONDS;
263			case US: return MICROSECONDS;
264			case MS: return MILLISECONDS;
265			case S: return SECONDS;
266			default: assert(false); return null;
267			}
268	dl	1.9	}
269	tim	1.1	}