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>The <tt>TimeUnit</tt> 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
 * @spec JSR-166
 * @revised $Date: 2003/08/06 16:08:49 $
 * @editor $Author: dl $
 * @author Doug Lea
 */
public final class TimeUnit implements java.io.Serializable {

    /**
     * Convert the given time duration in the given unit to the
     * current unit.  Conversions from finer to coarser granulaties
     * truncate, so lose precision. Conversions from coarser to finer
     * granularities may numerically overflow.
     *
     * @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.
     */
    public long convert(long duration, TimeUnit unit) {
        if (unit == this)
            return duration;
        if (index > unit.index)
            return duration / multipliers[index - unit.index];
        else
            return duration * multipliers[unit.index - index];
    }

    /**
     * Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
     * @param duration the duration
     * @return the converted duration.
     **/
    public long toNanos(long duration) {
        if (index == NS)
            return duration;
        else
            return duration * multipliers[index];
    }

    /**
     * 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 {
        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 {
        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 {
        long ms = MILLISECONDS.convert(timeout, this);
        int ns = excessNanos(timeout, ms);
        Thread.sleep(ms, ns);
    }

    /* 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 */
    static final int[] multipliers = { 1, 1000, 1000*1000, 1000*1000*1000 };

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

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

    /**
     * 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;
    }

    /** Unit for one-second granularities. */
    public static final TimeUnit SECONDS = new TimeUnit(S);

    /** Unit for one-millisecond granularities. */
    public static final TimeUnit MILLISECONDS = new TimeUnit(MS);

    /** Unit for one-microsecond granularities. */
    public static final TimeUnit MICROSECONDS = new TimeUnit(US);

    /** Unit for one-nanosecond granularities. */
    public static final TimeUnit NANOSECONDS = new TimeUnit(NS);

}
Revision:	1.8
Committed:	Wed Aug 6 18:22:09 2003 UTC (20 years, 10 months ago) by tim
Branch:	MAIN
CVS Tags:	JSR166_CR1
Changes since 1.7:	+6 -6 lines
Log Message:	Fixes to minor errors found by DocCheck
#	User	Rev	Content
1	dl	1.2	/*
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	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	tim	1.6	* <p>The <tt>TimeUnit</tt> class cannot be directly instantiated.
19	tim	1.1	* Use the {@link #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS},
20			* and {@link #NANOSECONDS} static instances that provide predefined
21			* units of precision. If you use these frequently, consider
22			* statically 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	tim	1.6	* the following code will timeout in 50 milliseconds if the {@link java.util.concurrent.locks.Lock lock}
27	tim	1.1	* 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	tim	1.6	* <pre>
33	tim	1.1	* 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			* @spec JSR-166
42	tim	1.8	* @revised $Date: 2003/08/06 16:08:49 $
43			* @editor $Author: dl $
44	dl	1.4	* @author Doug Lea
45	tim	1.1	*/
46			public final class TimeUnit implements java.io.Serializable {
47
48			/**
49			* Convert the given time duration in the given unit to the
50			* current unit. Conversions from finer to coarser granulaties
51			* truncate, so lose precision. Conversions from coarser to finer
52			* granularities may numerically overflow.
53			*
54			* @param duration the time duration in the given <tt>unit</tt>
55			* @param unit the unit of the <tt>duration</tt> argument
56			* @return the converted duration in the current unit.
57			*/
58			public long convert(long duration, TimeUnit unit) {
59	dl	1.2	if (unit == this)
60			return duration;
61	tim	1.6	if (index > unit.index)
62	tim	1.1	return duration / multipliers[index - unit.index];
63	tim	1.6	else
64	tim	1.1	return duration * multipliers[unit.index - index];
65	dl	1.2	}
66
67			/**
68	dholmes	1.3	* Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
69	dl	1.2	* @param duration the duration
70			* @return the converted duration.
71			**/
72			public long toNanos(long duration) {
73			if (index == NS)
74			return duration;
75			else
76			return duration * multipliers[index];
77	tim	1.1	}
78	tim	1.6
79	tim	1.1	/**
80	tim	1.6	* Perform a timed <tt>Object.wait</tt> using the current time unit.
81	tim	1.1	* This is a convenience method that converts timeout arguments into the
82	dl	1.7	* form required by the <tt>Object.wait</tt> method.
83	tim	1.1	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
84			* {@link BlockingQueue#poll BlockingQueue.poll} using:
85			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
86			* while (empty) {
87			* unit.timedWait(this, timeout);
88			* ...
89			* }
90			* }</pre>
91			* @param obj the object to wait on
92			* @param timeout the maximum time to wait
93			* @throws InterruptedException if interrupted while waiting.
94			* @see Object#wait(long, int)
95			*/
96			public void timedWait(Object obj, long timeout)
97			throws InterruptedException {
98			long ms = MILLISECONDS.convert(timeout, this);
99			int ns = excessNanos(timeout, ms);
100			obj.wait(ms, ns);
101			}
102
103			/**
104			* Perform a timed <tt>Thread.join</tt> using the current time unit.
105			* This is a convenience method that converts time arguments into the
106			* form required by the <tt>Thread.join</tt> method.
107			* @param thread the thread to wait for
108			* @param timeout the maximum time to wait
109			* @throws InterruptedException if interrupted while waiting.
110			* @see Thread#join(long, int)
111			*/
112			public void timedJoin(Thread thread, long timeout)
113			throws InterruptedException {
114			long ms = MILLISECONDS.convert(timeout, this);
115			int ns = excessNanos(timeout, ms);
116			thread.join(ms, ns);
117			}
118	tim	1.6
119	tim	1.1	/**
120			* Perform a <tt>Thread.sleep</tt> using the current time unit.
121			* This is a convenience method that converts time arguments into the
122			* form required by the <tt>Thread.sleep</tt> method.
123	tim	1.6	* @param timeout the minimum time to sleep
124	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
125			* @see Thread#sleep
126			*/
127			public void sleep(long timeout) throws InterruptedException {
128			long ms = MILLISECONDS.convert(timeout, this);
129			int ns = excessNanos(timeout, ms);
130			Thread.sleep(ms, ns);
131			}
132
133			/* ordered indices for each time unit */
134			private static final int NS = 0;
135			private static final int US = 1;
136			private static final int MS = 2;
137			private static final int S = 3;
138
139	dl	1.4	/** quick lookup table for conversion factors */
140	tim	1.1	static final int[] multipliers = { 1, 1000, 10001000, 10001000*1000 };
141
142	dl	1.4	/** the index of this unit */
143	tim	1.1	int index;
144
145			/** private constructor */
146			TimeUnit(int index) { this.index = index; }
147
148	tim	1.6	/**
149	tim	1.1	* Utility method to compute the excess-nanosecond argument to
150	dl	1.7	* wait, sleep, join. The results may overflow, so public methods
151			* invoking this should document possible overflow unless
152			* overflow is known not to be possible for the given arguments.
153	tim	1.1	*/
154			private int excessNanos(long time, long ms) {
155	tim	1.6	if (index == NS)
156	tim	1.1	return (int) (time - (ms * multipliers[MS-NS]));
157	tim	1.6	else if (index == US)
158	tim	1.1	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
159	tim	1.6	else
160	tim	1.1	return 0;
161			}
162
163	tim	1.8	/** Unit for one-second granularities. */
164	tim	1.1	public static final TimeUnit SECONDS = new TimeUnit(S);
165
166	tim	1.8	/** Unit for one-millisecond granularities. */
167	tim	1.1	public static final TimeUnit MILLISECONDS = new TimeUnit(MS);
168
169	tim	1.8	/** Unit for one-microsecond granularities. */
170	tim	1.1	public static final TimeUnit MICROSECONDS = new TimeUnit(US);
171
172	tim	1.8	/** Unit for one-nanosecond granularities. */
173	tim	1.1	public static final TimeUnit NANOSECONDS = new TimeUnit(NS);
174
175			}