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 methods which
 * can timeout, 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:	1.18
Committed:	Sat Dec 27 19:26:26 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
Changes since 1.17:	+2 -2 lines
Log Message:	Headers reference Creative Commons
#	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.
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	* various contexts.
17	*
18	* <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	*
24	* <p>A <tt>TimeUnit</tt> is mainly used to inform blocking methods which
25	* can timeout, how the timeout parameter should be interpreted. For example,
26	* the following code will timeout in 50 milliseconds if the {@link java.util.concurrent.locks.Lock lock}
27	* is not available:
28	* <pre> Lock lock = ...;
29	* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
30	* </pre>
31	* while this code will timeout in 50 seconds:
32	* <pre>
33	* Lock lock = ...;
34	* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
35	* </pre>
36	*
37	* Note however, that there is no guarantee that a particular timeout
38	* implementation will be able to notice the passage of time at the
39	* same granularity as the given <tt>TimeUnit</tt>.
40	*
41	* @since 1.5
42	* @author Doug Lea
43	*/
44	public final class TimeUnit implements java.io.Serializable {
45	/* ordered indices for each time unit */
46	private static final int NS = 0;
47	private static final int US = 1;
48	private static final int MS = 2;
49	private static final int S = 3;
50
51	/** quick lookup table for conversion factors */
52	private static final int[] multipliers = { 1,
53	1000,
54	1000*1000,
55	100010001000 };
56
57	/** lookup table to check saturation */
58	private static final long[] overflows = {
59	// Note that because we are dividing these down anyway,
60	// we don't have to deal with asymmetry of MIN/MAX values.
61	0, // unused
62	Long.MAX_VALUE / 1000,
63	Long.MAX_VALUE / (1000 * 1000),
64	Long.MAX_VALUE / (1000 * 1000 * 1000) };
65
66	/** the index of this unit */
67	private int index;
68	/** Common name for unit */
69	private final String unitName;
70
71	/** private constructor */
72	TimeUnit(int index, String name) {
73	this.index = index;
74	this.unitName = name;
75	}
76
77	/** Unit for one-second granularities. */
78	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
79	/** Unit for one-millisecond granularities. */
80	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
81	/** Unit for one-microsecond granularities. */
82	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
83	/** Unit for one-nanosecond granularities. */
84	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
85
86	/**
87	* Utility method to compute the excess-nanosecond argument to
88	* wait, sleep, join.
89	*/
90	private int excessNanos(long time, long ms) {
91	if (index == NS)
92	return (int) (time - (ms * multipliers[MS-NS]));
93	else if (index == US)
94	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
95	else
96	return 0;
97	}
98
99	/**
100	* Perform conversion based on given delta representing the
101	* difference between units
102	* @param delta the difference in index values of source and target units
103	* @param duration the duration
104	* @return converted duration or saturated value
105	*/
106	private static long doConvert(int delta, long duration) {
107	if (delta == 0)
108	return duration;
109	if (delta < 0)
110	return duration / multipliers[-delta];
111	if (duration > overflows[delta])
112	return Long.MAX_VALUE;
113	if (duration < -overflows[delta])
114	return Long.MIN_VALUE;
115	return duration * multipliers[delta];
116	}
117
118	/**
119	* Convert the given time duration in the given unit to this
120	* unit. Conversions from finer to coarser granularities
121	* truncate, so lose precision. For example converting
122	* <tt>999</tt> milliseconds to seconds results in
123	* <tt>0</tt>. Conversions from coarser to finer granularities
124	* with arguments that would numerically overflow saturate to
125	* <tt>Long.MIN_VALUE</tt> if negative or <tt>Long.MAX_VALUE</tt>
126	* if positive.
127	*
128	* @param duration the time duration in the given <tt>unit</tt>
129	* @param unit the unit of the <tt>duration</tt> argument
130	* @return the converted duration in this unit,
131	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
132	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
133	*/
134	public long convert(long duration, TimeUnit unit) {
135	return doConvert(unit.index - index, duration);
136	}
137
138	/**
139	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
140	* @param duration the duration
141	* @return the converted duration,
142	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
143	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
144	* @see #convert
145	*/
146	public long toNanos(long duration) {
147	return doConvert(index, duration);
148	}
149
150	/**
151	* Equivalent to <tt>MICROSECONDS.convert(duration, this)</tt>.
152	* @param duration the duration
153	* @return the converted duration,
154	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
155	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
156	* @see #convert
157	*/
158	public long toMicros(long duration) {
159	return doConvert(index - US, duration);
160	}
161
162	/**
163	* Equivalent to <tt>MILLISECONDS.convert(duration, this)</tt>.
164	* @param duration the duration
165	* @return the converted duration,
166	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
167	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
168	* @see #convert
169	*/
170	public long toMillis(long duration) {
171	return doConvert(index - MS, duration);
172	}
173
174	/**
175	* Equivalent to <tt>SECONDS.convert(duration, this)</tt>.
176	* @param duration the duration
177	* @return the converted duration.
178	* @see #convert
179	*/
180	public long toSeconds(long duration) {
181	return doConvert(index - S, duration);
182	}
183
184	/**
185	* Perform a timed <tt>Object.wait</tt> using this time unit.
186	* This is a convenience method that converts timeout arguments into the
187	* form required by the <tt>Object.wait</tt> method.
188	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
189	* {@link BlockingQueue#poll BlockingQueue.poll} using:
190	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
191	* while (empty) {
192	* unit.timedWait(this, timeout);
193	* ...
194	* }
195	* }</pre>
196	* @param obj the object to wait on
197	* @param timeout the maximum time to wait.
198	* @throws InterruptedException if interrupted while waiting.
199	* @see Object#wait(long, int)
200	*/
201	public void timedWait(Object obj, long timeout)
202	throws InterruptedException {
203	if (timeout > 0) {
204	long ms = toMillis(timeout);
205	int ns = excessNanos(timeout, ms);
206	obj.wait(ms, ns);
207	}
208	}
209
210	/**
211	* Perform a timed <tt>Thread.join</tt> using this time unit.
212	* This is a convenience method that converts time arguments into the
213	* form required by the <tt>Thread.join</tt> method.
214	* @param thread the thread to wait for
215	* @param timeout the maximum time to wait
216	* @throws InterruptedException if interrupted while waiting.
217	* @see Thread#join(long, int)
218	*/
219	public void timedJoin(Thread thread, long timeout)
220	throws InterruptedException {
221	if (timeout > 0) {
222	long ms = toMillis(timeout);
223	int ns = excessNanos(timeout, ms);
224	thread.join(ms, ns);
225	}
226	}
227
228	/**
229	* Perform a <tt>Thread.sleep</tt> using this unit.
230	* This is a convenience method that converts time arguments into the
231	* form required by the <tt>Thread.sleep</tt> method.
232	* @param timeout the minimum time to sleep
233	* @throws InterruptedException if interrupted while sleeping.
234	* @see Thread#sleep
235	*/
236	public void sleep(long timeout) throws InterruptedException {
237	if (timeout > 0) {
238	long ms = toMillis(timeout);
239	int ns = excessNanos(timeout, ms);
240	Thread.sleep(ms, ns);
241	}
242	}
243
244	/**
245	* Return the common name for this unit.
246	*/
247	public String toString() {
248	return unitName;
249	}
250
251	/**
252	* Resolves instances being deserialized to a single instance per
253	* unit.
254	*/
255	private Object readResolve() {
256	switch(index) {
257	case NS: return NANOSECONDS;
258	case US: return MICROSECONDS;
259	case MS: return MILLISECONDS;
260	case S: return SECONDS;
261	default: assert(false); return null;
262	}
263	}
264	}