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:	1.21
Committed:	Mon Feb 9 00:23:55 2004 UTC (20 years, 3 months ago) by dl
Branch:	MAIN
CVS Tags:	JSR166_PFD
Changes since 1.20:	+1 -1 lines
Log Message:	Wording improvements and fixes
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/licenses/publicdomain
5	*/
6
7	package java.util.concurrent;
8
9	/**
10	* 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. 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	*
17	* <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	*
22	* <pre> Lock lock = ...;
23	* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
24	* </pre>
25	* while this code will timeout in 50 seconds:
26	* <pre>
27	* Lock lock = ...;
28	* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
29	* </pre>
30	*
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	*
35	* @since 1.5
36	* @author Doug Lea
37	*/
38	public enum TimeUnit {
39	NANOSECONDS(0), MICROSECONDS(1), MILLISECONDS(2), SECONDS(3);
40
41	/** the index of this unit */
42	private final int index;
43
44	/** Internal constructor */
45	TimeUnit(int index) {
46	this.index = index;
47	}
48
49	/** 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	*/
62	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
69	/**
70	* Perform conversion based on given delta representing the
71	* 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	* Convert the given time duration in the given unit to this
90	* unit. Conversions from finer to coarser granularities
91	* 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	*
98	* @param duration the time duration in the given <tt>unit</tt>
99	* @param unit the unit of the <tt>duration</tt> argument
100	* @return the converted duration in this unit,
101	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
102	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
103	*/
104	public long convert(long duration, TimeUnit unit) {
105	return doConvert(unit.index - index, duration);
106	}
107
108	/**
109	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
110	* @param duration the duration
111	* @return the converted duration,
112	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
113	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
114	* @see #convert
115	*/
116	public long toNanos(long duration) {
117	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	return doConvert(index - MICROSECONDS.index, duration);
130	}
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	return doConvert(index - MILLISECONDS.index, duration);
142	}
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	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	}
166
167	/**
168	* Perform a timed <tt>Object.wait</tt> using this time unit.
169	* 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	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
177	* while (empty) {
178	* unit.timedWait(this, timeout);
179	* ...
180	* }
181	* }</pre>
182	*
183	* @param obj the object to wait on
184	* @param timeout the maximum time to wait.
185	* @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	if (timeout > 0) {
191	long ms = toMillis(timeout);
192	int ns = excessNanos(timeout, ms);
193	obj.wait(ms, ns);
194	}
195	}
196
197	/**
198	* Perform a timed <tt>Thread.join</tt> using this time unit.
199	* 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	if (timeout > 0) {
209	long ms = toMillis(timeout);
210	int ns = excessNanos(timeout, ms);
211	thread.join(ms, ns);
212	}
213	}
214
215	/**
216	* Perform a <tt>Thread.sleep</tt> using this unit.
217	* This is a convenience method that converts time arguments into the
218	* form required by the <tt>Thread.sleep</tt> method.
219	* @param timeout the minimum time to sleep
220	* @throws InterruptedException if interrupted while sleeping.
221	* @see Thread#sleep
222	*/
223	public void sleep(long timeout) throws InterruptedException {
224	if (timeout > 0) {
225	long ms = toMillis(timeout);
226	int ns = excessNanos(timeout, ms);
227	Thread.sleep(ms, ns);
228	}
229	}
230
231	}