util/concurrent/TimeUnit.java

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.
 * A static method {@link #highResolutionTime} provides access to a high
 * resolution, nanosecond, timer, which can be used to measure elapsed time.
 *
 * <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 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: 2003/03/29 02:17:05 $
 * @editor $Author: dholmes $
 *
 * @fixme The previous version created singleton subclass instances. I could
 * not see any reason to create subclasses instead of just instances.
 * Neither approach allows creation of your own units.
 */
public final class TimeUnit implements java.io.Serializable {

    /**
     * Return the current value of the system high resolution timer, in
     * nanoseconds. This method can only be used to measure elapsed time
     * and is not related to any notion of system, or wall-clock time.
     * Although the value returned represents nanoseconds since some
     * arbitrary start time in the past, the resolution at which this value
     * is updated is not specified. So we have nanosecond precision, but
     * not necessarily nanosecond accuracy.
     * It is guaranteed that successive return
     * values from this method will not decrease.
     *
     * <p> For example to measure how long some code takes to execute, 
     * with nanosecond precision:
     * <pre>
     * long startTime = TimeUnit.highResolutionTime();
     * // ... the code being measured ...
     * long estimatedTime = TimeUnit.highResolutionTime() - startTime;
     * </pre>
     * 
     * @return The current value of the system high resolution timer, in
     * nanoseconds.
     *
     * @fixme Is this spec tight enough? Too tight? What about issues of
     * reading the TSC from different processors on a SMP?
     */
    public static final long highResolutionTime() {
        return systemTimeNanos();
    }

    /**
     * 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 (index > unit.index) {
            return duration / multipliers[index - unit.index];
        }
        else {
            return duration * multipliers[unit.index - 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 time 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.
     * @fixme overflow?
     */
    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;
    }

    /** Underlying native time call */
    static native long systemTimeNanos();

    /** 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:	1.1
Committed:	Wed May 14 21:30:48 2003 UTC (21 years ago) by tim
Branch:	MAIN
Log Message:	Moved main source rooted at . to ./src/main Moved test source rooted at ./etc/testcases to ./src/test
#	User	Rev	Content
1	tim	1.1	package java.util.concurrent;
2
3			/**
4			* A <tt>TimeUnit</tt> represents time durations at a given unit of
5			* granularity and provides utility methods to convert across units,
6			* and to perform timing and delay operations in these units.
7			* <tt>TimeUnit</tt> is a "featherweight" class.
8			* It does not maintain time information, but only helps organize and
9			* use time representations that may be maintained separately across
10			* various contexts.
11			* A static method {@link #highResolutionTime} provides access to a high
12			* resolution, nanosecond, timer, which can be used to measure elapsed time.
13			*
14			* <p>The <tt>TimeUnit</tt> class cannot be directly instantiated.
15			* Use the {@link #SECONDS}, {@link #MILLISECONDS}, {@link #MICROSECONDS},
16			* and {@link #NANOSECONDS} static instances that provide predefined
17			* units of precision. If you use these frequently, consider
18			* statically importing this class.
19			*
20			* <p>A <tt>TimeUnit</tt> is mainly used to inform blocking methods which
21			* can timeout, how the timeout parameter should be interpreted. For example,
22			* the following code will timeout in 50 milliseconds if the {@link Lock lock}
23			* is not available:
24			* <pre> Lock lock = ...;
25			* if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ...
26			* </pre>
27			* while this code will timeout in 50 seconds:
28			* <pre>
29			* Lock lock = ...;
30			* if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ...
31			* </pre>
32			* Note however, that there is no guarantee that a particular lock, in this
33			* case, will be able to notice the passage of time at the same granularity
34			* as the given <tt>TimeUnit</tt>.
35			*
36			* @since 1.5
37			* @spec JSR-166
38			* @revised $Date: 2003/03/29 02:17:05 $
39			* @editor $Author: dholmes $
40			*
41			* @fixme The previous version created singleton subclass instances. I could
42			* not see any reason to create subclasses instead of just instances.
43			* Neither approach allows creation of your own units.
44			*/
45			public final class TimeUnit implements java.io.Serializable {
46
47			/**
48			* Return the current value of the system high resolution timer, in
49			* nanoseconds. This method can only be used to measure elapsed time
50			* and is not related to any notion of system, or wall-clock time.
51			* Although the value returned represents nanoseconds since some
52			* arbitrary start time in the past, the resolution at which this value
53			* is updated is not specified. So we have nanosecond precision, but
54			* not necessarily nanosecond accuracy.
55			* It is guaranteed that successive return
56			* values from this method will not decrease.
57			*
58			* <p> For example to measure how long some code takes to execute,
59			* with nanosecond precision:
60			* <pre>
61			* long startTime = TimeUnit.highResolutionTime();
62			* // ... the code being measured ...
63			* long estimatedTime = TimeUnit.highResolutionTime() - startTime;
64			* </pre>
65			*
66			* @return The current value of the system high resolution timer, in
67			* nanoseconds.
68			*
69			* @fixme Is this spec tight enough? Too tight? What about issues of
70			* reading the TSC from different processors on a SMP?
71			*/
72			public static final long highResolutionTime() {
73			return systemTimeNanos();
74			}
75
76			/**
77			* Convert the given time duration in the given unit to the
78			* current unit. Conversions from finer to coarser granulaties
79			* truncate, so lose precision. Conversions from coarser to finer
80			* granularities may numerically overflow.
81			*
82			* @param duration the time duration in the given <tt>unit</tt>
83			* @param unit the unit of the <tt>duration</tt> argument
84			* @return the converted duration in the current unit.
85			*/
86			public long convert(long duration, TimeUnit unit) {
87			if (index > unit.index) {
88			return duration / multipliers[index - unit.index];
89			}
90			else {
91			return duration * multipliers[unit.index - index];
92			}
93			}
94
95			/**
96			* Perform a timed <tt>Object.wait</tt> using the current time unit.
97			* This is a convenience method that converts timeout arguments into the
98			* form required by the <tt>Object.wait</tt> method.
99			* <p>For example, you could implement a blocking <tt>poll</tt> method (see
100			* {@link BlockingQueue#poll BlockingQueue.poll} using:
101			* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
102			* while (empty) {
103			* unit.timedWait(this, timeout);
104			* ...
105			* }
106			* }</pre>
107			* @param obj the object to wait on
108			* @param timeout the maximum time to wait
109			* @throws InterruptedException if interrupted while waiting.
110			* @see Object#wait(long, int)
111			*/
112			public void timedWait(Object obj, long timeout)
113			throws InterruptedException {
114			long ms = MILLISECONDS.convert(timeout, this);
115			int ns = excessNanos(timeout, ms);
116			obj.wait(ms, ns);
117			}
118
119			/**
120			* Perform a timed <tt>Thread.join</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.join</tt> method.
123			* @param thread the thread to wait for
124			* @param timeout the maximum time to wait
125			* @throws InterruptedException if interrupted while waiting.
126			* @see Thread#join(long, int)
127			*/
128			public void timedJoin(Thread thread, long timeout)
129			throws InterruptedException {
130			long ms = MILLISECONDS.convert(timeout, this);
131			int ns = excessNanos(timeout, ms);
132			thread.join(ms, ns);
133			}
134
135			/**
136			* Perform a <tt>Thread.sleep</tt> using the current time unit.
137			* This is a convenience method that converts time arguments into the
138			* form required by the <tt>Thread.sleep</tt> method.
139			* @param time the minimum time to sleep
140			* @throws InterruptedException if interrupted while sleeping.
141			* @see Thread#sleep
142			*/
143			public void sleep(long timeout) throws InterruptedException {
144			long ms = MILLISECONDS.convert(timeout, this);
145			int ns = excessNanos(timeout, ms);
146			Thread.sleep(ms, ns);
147			}
148
149			/* ordered indices for each time unit */
150			private static final int NS = 0;
151			private static final int US = 1;
152			private static final int MS = 2;
153			private static final int S = 3;
154
155			/* quick lookup table for conversion factors */
156			static final int[] multipliers = { 1, 1000, 10001000, 10001000*1000 };
157
158			/* the index of this unit */
159			int index;
160
161			/** private constructor */
162			TimeUnit(int index) { this.index = index; }
163
164			/**
165			* Utility method to compute the excess-nanosecond argument to
166			* wait, sleep, join.
167			* @fixme overflow?
168			*/
169			private int excessNanos(long time, long ms) {
170			if (index == NS)
171			return (int) (time - (ms * multipliers[MS-NS]));
172			else if (index == US)
173			return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
174			else
175			return 0;
176			}
177
178			/** Underlying native time call */
179			static native long systemTimeNanos();
180
181			/** Unit for one-second granularities */
182			public static final TimeUnit SECONDS = new TimeUnit(S);
183
184			/** Unit for one-millisecond granularities */
185			public static final TimeUnit MILLISECONDS = new TimeUnit(MS);
186
187			/** Unit for one-microsecond granularities */
188			public static final TimeUnit MICROSECONDS = new TimeUnit(US);
189
190			/** Unit for one-nanosecond granularities */
191			public static final TimeUnit NANOSECONDS = new TimeUnit(NS);
192
193			}