util/concurrent/TimeUnit.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

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 lock, in this
 * case, 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. The results may overflow, so public methods
     * invoking this should document possible overflow unless
     * overflow is known not to be possible for the given arguments.
     */
    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 the
     * current unit.  Conversions from finer to coarser granulaties
     * 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 the current 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 the current 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 = MILLISECONDS.convert(timeout, this);
            int ns = excessNanos(timeout, ms);
            obj.wait(ms, ns);
        }
    }

    /**
     * Perform a timed <tt>Thread.join</tt> using the current 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 = MILLISECONDS.convert(timeout, this);
            int ns = excessNanos(timeout, ms);
            thread.join(ms, ns);
        }
    }

    /**
     * Perform a <tt>Thread.sleep</tt> using the current time 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 = MILLISECONDS.convert(timeout, this);
            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:	1.14
Committed:	Fri Sep 12 20:17:50 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.13:	+66 -78 lines
Log Message:	Use readResolve to deserialize
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain. Use, modify, and
4	* redistribute this code in any way without acknowledgement.
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	* Note however, that there is no guarantee that a particular lock, in this
37	* case, will be able to notice the passage of time at the same granularity
38	* as the given <tt>TimeUnit</tt>.
39	*
40	* @since 1.5
41	* @author Doug Lea
42	*/
43	public final class TimeUnit implements java.io.Serializable {
44	/* ordered indices for each time unit */
45	private static final int NS = 0;
46	private static final int US = 1;
47	private static final int MS = 2;
48	private static final int S = 3;
49
50	/** quick lookup table for conversion factors */
51	private static final int[] multipliers = { 1,
52	1000,
53	1000*1000,
54	100010001000 };
55
56	/** lookup table to check saturation */
57	private static final long[] overflows = {
58	// Note that because we are dividing these down anyway,
59	// we don't have to deal with asymmetry of MIN/MAX values.
60	0, // unused
61	Long.MAX_VALUE / 1000,
62	Long.MAX_VALUE / (1000 * 1000),
63	Long.MAX_VALUE / (1000 * 1000 * 1000) };
64
65	/** the index of this unit */
66	private int index;
67	/** Common name for unit */
68	private final String unitName;
69
70	/** private constructor */
71	TimeUnit(int index, String name) {
72	this.index = index;
73	this.unitName = name;
74	}
75
76	/** Unit for one-second granularities. */
77	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
78	/** Unit for one-millisecond granularities. */
79	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
80	/** Unit for one-microsecond granularities. */
81	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
82	/** Unit for one-nanosecond granularities. */
83	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
84
85	/**
86	* Utility method to compute the excess-nanosecond argument to
87	* wait, sleep, join. The results may overflow, so public methods
88	* invoking this should document possible overflow unless
89	* overflow is known not to be possible for the given arguments.
90	*/
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
100	/**
101	* Perform conversion based on given delta representing the
102	* 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	* Convert the given time duration in the given unit to the
121	* current unit. Conversions from finer to coarser granulaties
122	* 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	*
129	* @param duration the time duration in the given <tt>unit</tt>
130	* @param unit the unit of the <tt>duration</tt> argument
131	* @return the converted duration in the current unit,
132	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
133	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
134	*/
135	public long convert(long duration, TimeUnit unit) {
136	return doConvert(unit.index - index, duration);
137	}
138
139	/**
140	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
141	* @param duration the duration
142	* @return the converted duration,
143	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
144	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
145	* @see #convert
146	*/
147	public long toNanos(long duration) {
148	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	}
184
185	/**
186	* Perform a timed <tt>Object.wait</tt> using the current time unit.
187	* This is a convenience method that converts timeout arguments into the
188	* form required by the <tt>Object.wait</tt> method.
189	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
190	* {@link BlockingQueue#poll BlockingQueue.poll} using:
191	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
192	* while (empty) {
193	* unit.timedWait(this, timeout);
194	* ...
195	* }
196	* }</pre>
197	* @param obj the object to wait on
198	* @param timeout the maximum time to wait.
199	* @throws InterruptedException if interrupted while waiting.
200	* @see Object#wait(long, int)
201	*/
202	public void timedWait(Object obj, long timeout)
203	throws InterruptedException {
204	if (timeout > 0) {
205	long ms = MILLISECONDS.convert(timeout, this);
206	int ns = excessNanos(timeout, ms);
207	obj.wait(ms, ns);
208	}
209	}
210
211	/**
212	* Perform a timed <tt>Thread.join</tt> using the current time unit.
213	* This is a convenience method that converts time arguments into the
214	* form required by the <tt>Thread.join</tt> method.
215	* @param thread the thread to wait for
216	* @param timeout the maximum time to wait
217	* @throws InterruptedException if interrupted while waiting.
218	* @see Thread#join(long, int)
219	*/
220	public void timedJoin(Thread thread, long timeout)
221	throws InterruptedException {
222	if (timeout > 0) {
223	long ms = MILLISECONDS.convert(timeout, this);
224	int ns = excessNanos(timeout, ms);
225	thread.join(ms, ns);
226	}
227	}
228
229	/**
230	* Perform a <tt>Thread.sleep</tt> using the current time unit.
231	* This is a convenience method that converts time arguments into the
232	* form required by the <tt>Thread.sleep</tt> method.
233	* @param timeout the minimum time to sleep
234	* @throws InterruptedException if interrupted while sleeping.
235	* @see Thread#sleep
236	*/
237	public void sleep(long timeout) throws InterruptedException {
238	if (timeout > 0) {
239	long ms = MILLISECONDS.convert(timeout, this);
240	int ns = excessNanos(timeout, ms);
241	Thread.sleep(ms, ns);
242	}
243	}
244
245	/**
246	* Return the common name for this unit.
247	*/
248	public String toString() {
249	return unitName;
250	}
251
252	/**
253	* Resolves instances being deserialized to a single instance per
254	* unit.
255	*/
256	private Object readResolve() {
257	switch(index) {
258	case NS: return NANOSECONDS;
259	case US: return MICROSECONDS;
260	case MS: return MILLISECONDS;
261	case S: return SECONDS;
262	default: assert(false); return null;
263	}
264	}
265	}