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: 2003/07/12 00:50:34 $
 * @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.
     * @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;
    }

    /** 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:	1.6
Committed:	Thu Jul 31 20:32:00 2003 UTC (20 years, 10 months ago) by tim
Branch:	MAIN
Changes since 1.5:	+20 -20 lines
Log Message:	More javadoc link fixes
#	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>The <tt>TimeUnit</tt> class cannot be directly instantiated.
19	* 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	* 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	* @spec JSR-166
42	* @revised $Date: 2003/07/12 00:50:34 $
43	* @editor $Author: dl $
44	* @author Doug Lea
45	*/
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	if (unit == this)
60	return duration;
61	if (index > unit.index)
62	return duration / multipliers[index - unit.index];
63	else
64	return duration * multipliers[unit.index - index];
65	}
66
67	/**
68	* Equivalent to <code>NANOSECONDS.convert(duration, this)</code>.
69	* @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	}
78
79	/**
80	* Perform a timed <tt>Object.wait</tt> using the current time unit.
81	* This is a convenience method that converts timeout arguments into the
82	* form required by the <tt>Object.wait</tt> method.
83	* <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
119	/**
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	* @param timeout the minimum time to sleep
124	* @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	/** quick lookup table for conversion factors */
140	static final int[] multipliers = { 1, 1000, 10001000, 10001000*1000 };
141
142	/** the index of this unit */
143	int index;
144
145	/** private constructor */
146	TimeUnit(int index) { this.index = index; }
147
148	/**
149	* Utility method to compute the excess-nanosecond argument to
150	* wait, sleep, join.
151	* @fixme overflow?
152	*/
153	private int excessNanos(long time, long ms) {
154	if (index == NS)
155	return (int) (time - (ms * multipliers[MS-NS]));
156	else if (index == US)
157	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
158	else
159	return 0;
160	}
161
162	/** Unit for one-second granularities */
163	public static final TimeUnit SECONDS = new TimeUnit(S);
164
165	/** Unit for one-millisecond granularities */
166	public static final TimeUnit MILLISECONDS = new TimeUnit(MS);
167
168	/** Unit for one-microsecond granularities */
169	public static final TimeUnit MICROSECONDS = new TimeUnit(US);
170
171	/** Unit for one-nanosecond granularities */
172	public static final TimeUnit NANOSECONDS = new TimeUnit(NS);
173
174	}