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.  A
 * <tt>TimeUnit</tt> does not maintain time information, but only
 * helps organize and use time representations that may be maintained
 * separately across various contexts.
 *
 * <p>A <tt>TimeUnit</tt> is mainly used to inform time-based methods
 * how a given timing 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 enum TimeUnit {
    NANOSECONDS(0), MICROSECONDS(1), MILLISECONDS(2), SECONDS(3);

    /** the index of this unit */
    private final int index;

    /** Internal constructor */
    TimeUnit(int index) { 
        this.index = index; 
    }

    /** Lookup table for conversion factors */
    private static final int[] multipliers = { 
        1, 
        1000, 
        1000 * 1000, 
        1000 * 1000 * 1000 
    };
    
    /** 
     * Lookup table to check saturation.  Note that because we are
     * dividing these down, we don't have to deal with asymmetry of
     * MIN/MAX values.
     */
    private static final long[] overflows = { 
        0, // unused
        Long.MAX_VALUE / 1000,
        Long.MAX_VALUE / (1000 * 1000),
        Long.MAX_VALUE / (1000 * 1000 * 1000) 
    };

    /**
     * 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 - MICROSECONDS.index, 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 - MILLISECONDS.index, 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 - SECONDS.index, duration);
    }


    /**
     * Utility method to compute the excess-nanosecond argument to
     * wait, sleep, join.
     */
    private int excessNanos(long time, long ms) {
        if (this == NANOSECONDS)
            return (int) (time  - (ms * 1000 * 1000));
        if (this == MICROSECONDS)
            return (int) ((time * 1000) - (ms * 1000 * 1000));
        return 0;
    }

    /**
     * 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);
        }
    }

}
Revision:	1.20
Committed:	Tue Jan 13 12:59:26 2004 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.19:	+47 -85 lines
Log Message:	TimeUnit now an enum
#	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	dl	1.20	* and to perform timing and delay operations in these units. A
13			* <tt>TimeUnit</tt> does not maintain time information, but only
14			* helps organize and use time representations that may be maintained
15			* separately across various contexts.
16	tim	1.1	*
17	dl	1.20	* <p>A <tt>TimeUnit</tt> is mainly used to inform time-based methods
18			* how a given timing parameter should be interpreted. For example,
19			* the following code will timeout in 50 milliseconds if the {@link
20			* java.util.concurrent.locks.Lock lock} is not available:
21	dl	1.19	*
22	tim	1.1	* <pre> Lock lock = ...;
23			* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
24			* </pre>
25			* while this code will timeout in 50 seconds:
26	tim	1.6	* <pre>
27	tim	1.1	* Lock lock = ...;
28			* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
29			* </pre>
30	dl	1.15	*
31			* Note however, that there is no guarantee that a particular timeout
32			* implementation will be able to notice the passage of time at the
33			* same granularity as the given <tt>TimeUnit</tt>.
34	tim	1.1	*
35			* @since 1.5
36	dl	1.4	* @author Doug Lea
37	tim	1.1	*/
38	dl	1.20	public enum TimeUnit {
39			NANOSECONDS(0), MICROSECONDS(1), MILLISECONDS(2), SECONDS(3);
40	dl	1.14
41			/** the index of this unit */
42	dl	1.20	private final int index;
43	dl	1.14
44	dl	1.20	/** Internal constructor */
45			TimeUnit(int index) {
46	dl	1.14	this.index = index;
47			}
48
49	dl	1.20	/** Lookup table for conversion factors */
50			private static final int[] multipliers = {
51			1,
52			1000,
53			1000 * 1000,
54			1000 * 1000 * 1000
55			};
56
57			/**
58			* Lookup table to check saturation. Note that because we are
59			* dividing these down, we don't have to deal with asymmetry of
60			* MIN/MAX values.
61	dl	1.14	*/
62	dl	1.20	private static final long[] overflows = {
63			0, // unused
64			Long.MAX_VALUE / 1000,
65			Long.MAX_VALUE / (1000 * 1000),
66			Long.MAX_VALUE / (1000 * 1000 * 1000)
67			};
68	tim	1.1
69			/**
70	dl	1.14	* Perform conversion based on given delta representing the
71	dl	1.13	* difference between units
72			* @param delta the difference in index values of source and target units
73			* @param duration the duration
74			* @return converted duration or saturated value
75			*/
76			private static long doConvert(int delta, long duration) {
77			if (delta == 0)
78			return duration;
79			if (delta < 0)
80			return duration / multipliers[-delta];
81			if (duration > overflows[delta])
82			return Long.MAX_VALUE;
83			if (duration < -overflows[delta])
84			return Long.MIN_VALUE;
85			return duration * multipliers[delta];
86			}
87
88			/**
89	dl	1.17	* Convert the given time duration in the given unit to this
90			* unit. Conversions from finer to coarser granularities
91	dl	1.13	* truncate, so lose precision. For example converting
92			* <tt>999</tt> milliseconds to seconds results in
93			* <tt>0</tt>. Conversions from coarser to finer granularities
94			* with arguments that would numerically overflow saturate to
95			* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
96			* if positive.
97	tim	1.1	*
98			* @param duration the time duration in the given <tt>unit</tt>
99			* @param unit the unit of the <tt>duration</tt> argument
100	dl	1.17	* @return the converted duration in this unit,
101	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
102	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
103	tim	1.1	*/
104			public long convert(long duration, TimeUnit unit) {
105	dl	1.13	return doConvert(unit.index - index, duration);
106	dl	1.2	}
107
108			/**
109	dl	1.12	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
110	dl	1.2	* @param duration the duration
111	dl	1.13	* @return the converted duration,
112	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
113	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
114	dl	1.13	* @see #convert
115			*/
116	dl	1.2	public long toNanos(long duration) {
117	dl	1.13	return doConvert(index, duration);
118			}
119
120			/**
121			* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
122			* @param duration the duration
123			* @return the converted duration,
124			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
125			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
126			* @see #convert
127			*/
128			public long toMicros(long duration) {
129	dl	1.20	return doConvert(index - MICROSECONDS.index, duration);
130	dl	1.13	}
131
132			/**
133			* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
134			* @param duration the duration
135			* @return the converted duration,
136			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
137			* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
138			* @see #convert
139			*/
140			public long toMillis(long duration) {
141	dl	1.20	return doConvert(index - MILLISECONDS.index, duration);
142	dl	1.13	}
143
144			/**
145			* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
146			* @param duration the duration
147			* @return the converted duration.
148			* @see #convert
149			*/
150			public long toSeconds(long duration) {
151	dl	1.20	return doConvert(index - SECONDS.index, duration);
152			}
153
154
155			/**
156			* Utility method to compute the excess-nanosecond argument to
157			* wait, sleep, join.
158			*/
159			private int excessNanos(long time, long ms) {
160			if (this == NANOSECONDS)
161			return (int) (time - (ms * 1000 * 1000));
162			if (this == MICROSECONDS)
163			return (int) ((time * 1000) - (ms * 1000 * 1000));
164			return 0;
165	tim	1.1	}
166	tim	1.6
167	tim	1.1	/**
168	dl	1.17	* Perform a timed <tt>Object.wait</tt> using this time unit.
169	dl	1.19	* This is a convenience method that converts timeout arguments
170			* into the form required by the <tt>Object.wait</tt> method.
171			*
172			* <p>For example, you could implement a blocking <tt>poll</tt>
173			* method (see {@link BlockingQueue#poll BlockingQueue.poll}
174			* using:
175			*
176	tim	1.1	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
177			* while (empty) {
178			* unit.timedWait(this, timeout);
179			* ...
180			* }
181			* }</pre>
182	dl	1.19	*
183	tim	1.1	* @param obj the object to wait on
184	dl	1.10	* @param timeout the maximum time to wait.
185	tim	1.1	* @throws InterruptedException if interrupted while waiting.
186			* @see Object#wait(long, int)
187			*/
188			public void timedWait(Object obj, long timeout)
189			throws InterruptedException {
190	dl	1.10	if (timeout > 0) {
191	dl	1.15	long ms = toMillis(timeout);
192	dl	1.10	int ns = excessNanos(timeout, ms);
193			obj.wait(ms, ns);
194			}
195	tim	1.1	}
196
197			/**
198	dl	1.17	* Perform a timed <tt>Thread.join</tt> using this time unit.
199	tim	1.1	* This is a convenience method that converts time arguments into the
200			* form required by the <tt>Thread.join</tt> method.
201			* @param thread the thread to wait for
202			* @param timeout the maximum time to wait
203			* @throws InterruptedException if interrupted while waiting.
204			* @see Thread#join(long, int)
205			*/
206			public void timedJoin(Thread thread, 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			thread.join(ms, ns);
212			}
213	tim	1.1	}
214	tim	1.6
215	tim	1.1	/**
216	dl	1.17	* Perform a <tt>Thread.sleep</tt> using this unit.
217	tim	1.1	* This is a convenience method that converts time arguments into the
218			* form required by the <tt>Thread.sleep</tt> method.
219	tim	1.6	* @param timeout the minimum time to sleep
220	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
221			* @see Thread#sleep
222			*/
223			public void sleep(long timeout) throws InterruptedException {
224	dl	1.10	if (timeout > 0) {
225	dl	1.15	long ms = toMillis(timeout);
226	dl	1.10	int ns = excessNanos(timeout, ms);
227			Thread.sleep(ms, ns);
228			}
229	tim	1.1	}
230
231			}