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: 2003/08/30 14:52:52 $
 * @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 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) {
        if (unit == this)
            return duration;
        else if (index > unit.index) 
            return duration / multipliers[index - unit.index];
        else {
            int i = unit.index - index;
            if (duration > overflows[i])
                return Long.MAX_VALUE;
            if (duration < -overflows[i])
                return Long.MIN_VALUE;
            return duration * multipliers[i];
        }
    }

    /**
     * Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
     * @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.
     **/
    public long toNanos(long duration) {
        if (index == NS)
            return duration;
        if (duration > overflows[index])
            return Long.MAX_VALUE;
        if (duration < -overflows[index])
            return Long.MIN_VALUE;
        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 {
        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;
    }

    private final String unitName;

    /* 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 };

    /** lookup table to check saturation */
    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 */
    int index;

    /** private constructor */
    TimeUnit(int index, String name) { 
        this.index = index; 
        this.unitName = name;
    }

    /**
     * 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, "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");

}
Revision:	1.11
Committed:	Sat Aug 30 14:59:27 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.10:	+4 -4 lines
Log Message:	Fix typo
#	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	dl	1.11	* @revised $Date: 2003/08/30 14:52:52 $
43	dl	1.10	* @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	dl	1.10	* granularities with arguments that would numerically overflow
53			* saturate to <tt>Long.MIN_VALUE</tt> if negative or
54	dl	1.11	* <tt>Long.MAX_VALUE</tt> if positive.
55	tim	1.1	*
56			* @param duration the time duration in the given <tt>unit</tt>
57			* @param unit the unit of the <tt>duration</tt> argument
58	dl	1.10	* @return the converted duration in the current unit,
59			* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
60	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
61	tim	1.1	*/
62			public long convert(long duration, TimeUnit unit) {
63	dl	1.2	if (unit == this)
64			return duration;
65	dl	1.10	else if (index > unit.index)
66	tim	1.1	return duration / multipliers[index - unit.index];
67	dl	1.10	else {
68			int i = unit.index - index;
69			if (duration > overflows[i])
70			return Long.MAX_VALUE;
71			if (duration < -overflows[i])
72			return Long.MIN_VALUE;
73			return duration * multipliers[i];
74			}
75	dl	1.2	}
76
77			/**
78	dholmes	1.3	* Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
79	dl	1.2	* @param duration the duration
80			* @return the converted duration.
81	dl	1.10	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
82	dl	1.11	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
83	dl	1.2	**/
84			public long toNanos(long duration) {
85			if (index == NS)
86			return duration;
87	dl	1.10	if (duration > overflows[index])
88			return Long.MAX_VALUE;
89			if (duration < -overflows[index])
90			return Long.MIN_VALUE;
91			return duration * multipliers[index];
92	tim	1.1	}
93	tim	1.6
94	tim	1.1	/**
95	tim	1.6	* Perform a timed <tt>Object.wait</tt> using the current time unit.
96	tim	1.1	* This is a convenience method that converts timeout arguments into the
97	dl	1.7	* form required by the <tt>Object.wait</tt> method.
98	tim	1.1	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
99			* {@link BlockingQueue#poll BlockingQueue.poll} using:
100			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
101			* while (empty) {
102			* unit.timedWait(this, timeout);
103			* ...
104			* }
105			* }</pre>
106			* @param obj the object to wait on
107	dl	1.10	* @param timeout the maximum time to wait.
108	tim	1.1	* @throws InterruptedException if interrupted while waiting.
109			* @see Object#wait(long, int)
110			*/
111			public void timedWait(Object obj, long timeout)
112			throws InterruptedException {
113	dl	1.10	if (timeout > 0) {
114			long ms = MILLISECONDS.convert(timeout, this);
115			int ns = excessNanos(timeout, ms);
116			obj.wait(ms, ns);
117			}
118	tim	1.1	}
119
120			/**
121			* Perform a timed <tt>Thread.join</tt> using the current time unit.
122			* This is a convenience method that converts time arguments into the
123			* form required by the <tt>Thread.join</tt> method.
124			* @param thread the thread to wait for
125			* @param timeout the maximum time to wait
126			* @throws InterruptedException if interrupted while waiting.
127			* @see Thread#join(long, int)
128			*/
129			public void timedJoin(Thread thread, long timeout)
130			throws InterruptedException {
131	dl	1.10	if (timeout > 0) {
132			long ms = MILLISECONDS.convert(timeout, this);
133			int ns = excessNanos(timeout, ms);
134			thread.join(ms, ns);
135			}
136	tim	1.1	}
137	tim	1.6
138	tim	1.1	/**
139			* Perform a <tt>Thread.sleep</tt> using the current time unit.
140			* This is a convenience method that converts time arguments into the
141			* form required by the <tt>Thread.sleep</tt> method.
142	tim	1.6	* @param timeout the minimum time to sleep
143	tim	1.1	* @throws InterruptedException if interrupted while sleeping.
144			* @see Thread#sleep
145			*/
146			public void sleep(long timeout) throws InterruptedException {
147	dl	1.10	if (timeout > 0) {
148			long ms = MILLISECONDS.convert(timeout, this);
149			int ns = excessNanos(timeout, ms);
150			Thread.sleep(ms, ns);
151			}
152	tim	1.1	}
153
154	dl	1.9	/**
155			* Return the common name for this unit.
156			*/
157			public String toString() {
158			return unitName;
159			}
160
161			private final String unitName;
162
163	tim	1.1	/* ordered indices for each time unit */
164			private static final int NS = 0;
165			private static final int US = 1;
166			private static final int MS = 2;
167			private static final int S = 3;
168
169	dl	1.4	/** quick lookup table for conversion factors */
170	dl	1.10	static final int[] multipliers = { 1,
171			1000,
172			1000*1000,
173			100010001000 };
174
175			/** lookup table to check saturation */
176			static final long[] overflows = {
177			// Note that because we are dividing these down anyway,
178			// we don't have to deal with asymmetry of MIN/MAX values.
179			0, // unused
180			Long.MAX_VALUE / 1000,
181			Long.MAX_VALUE / (1000 * 1000),
182			Long.MAX_VALUE / (1000 * 1000 * 1000) };
183	tim	1.1
184	dl	1.4	/** the index of this unit */
185	tim	1.1	int index;
186
187			/** private constructor */
188	dl	1.9	TimeUnit(int index, String name) {
189			this.index = index;
190			this.unitName = name;
191			}
192	tim	1.1
193	tim	1.6	/**
194	tim	1.1	* Utility method to compute the excess-nanosecond argument to
195	dl	1.7	* wait, sleep, join. The results may overflow, so public methods
196			* invoking this should document possible overflow unless
197			* overflow is known not to be possible for the given arguments.
198	tim	1.1	*/
199			private int excessNanos(long time, long ms) {
200	tim	1.6	if (index == NS)
201	tim	1.1	return (int) (time - (ms * multipliers[MS-NS]));
202	tim	1.6	else if (index == US)
203	tim	1.1	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
204	tim	1.6	else
205	tim	1.1	return 0;
206			}
207
208	tim	1.8	/** Unit for one-second granularities. */
209	dl	1.9	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
210	tim	1.1
211	tim	1.8	/** Unit for one-millisecond granularities. */
212	dl	1.9	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
213	tim	1.1
214	tim	1.8	/** Unit for one-microsecond granularities. */
215	dl	1.9	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
216	tim	1.1
217	tim	1.8	/** Unit for one-nanosecond granularities. */
218	dl	1.9	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
219	tim	1.1
220			}