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 {

    /**
     * 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) {
        int i = unit.index - index;
        if (i == 0)
            return duration;
        if (i < 0) 
            return duration / multipliers[-i];
        if (duration > overflows[i])
            return Long.MAX_VALUE;
        if (duration < -overflows[i])
            return Long.MIN_VALUE;
        return duration * multipliers[i];
    }

    /**
     * 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.
     **/
    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:	1.12
Committed:	Sun Aug 31 13:33:14 2003 UTC (20 years, 9 months ago) by dl
Branch:	MAIN
Changes since 1.11:	+15 -20 lines
Log Message:	Removed non-standard tags and misc javadoc cleanup
#	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
45	/**
46	* Convert the given time duration in the given unit to the
47	* current unit. Conversions from finer to coarser granulaties
48	* truncate, so lose precision. Conversions from coarser to finer
49	* granularities with arguments that would numerically overflow
50	* saturate to <tt>Long.MIN_VALUE</tt> if negative or
51	* <tt>Long.MAX_VALUE</tt> if positive.
52	*
53	* @param duration the time duration in the given <tt>unit</tt>
54	* @param unit the unit of the <tt>duration</tt> argument
55	* @return the converted duration in the current unit,
56	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
57	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
58	*/
59	public long convert(long duration, TimeUnit unit) {
60	int i = unit.index - index;
61	if (i == 0)
62	return duration;
63	if (i < 0)
64	return duration / multipliers[-i];
65	if (duration > overflows[i])
66	return Long.MAX_VALUE;
67	if (duration < -overflows[i])
68	return Long.MIN_VALUE;
69	return duration * multipliers[i];
70	}
71
72	/**
73	* Equivalent to <tt>NANOSECONDS.convert(duration, this)</tt>.
74	* @param duration the duration
75	* @return the converted duration.
76	* or <tt>Long.MIN_VALUE</tt> if conversion would negatively
77	* overflow, or <tt>Long.MAX_VALUE</tt> if it would positively overflow.
78	**/
79	public long toNanos(long duration) {
80	if (index == NS)
81	return duration;
82	if (duration > overflows[index])
83	return Long.MAX_VALUE;
84	if (duration < -overflows[index])
85	return Long.MIN_VALUE;
86	return duration * multipliers[index];
87	}
88
89	/**
90	* Perform a timed <tt>Object.wait</tt> using the current time unit.
91	* This is a convenience method that converts timeout arguments into the
92	* form required by the <tt>Object.wait</tt> method.
93	* <p>For example, you could implement a blocking <tt>poll</tt> method (see
94	* {@link BlockingQueue#poll BlockingQueue.poll} using:
95	* <pre> public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
96	* while (empty) {
97	* unit.timedWait(this, timeout);
98	* ...
99	* }
100	* }</pre>
101	* @param obj the object to wait on
102	* @param timeout the maximum time to wait.
103	* @throws InterruptedException if interrupted while waiting.
104	* @see Object#wait(long, int)
105	*/
106	public void timedWait(Object obj, long timeout)
107	throws InterruptedException {
108	if (timeout > 0) {
109	long ms = MILLISECONDS.convert(timeout, this);
110	int ns = excessNanos(timeout, ms);
111	obj.wait(ms, ns);
112	}
113	}
114
115	/**
116	* Perform a timed <tt>Thread.join</tt> using the current time unit.
117	* This is a convenience method that converts time arguments into the
118	* form required by the <tt>Thread.join</tt> method.
119	* @param thread the thread to wait for
120	* @param timeout the maximum time to wait
121	* @throws InterruptedException if interrupted while waiting.
122	* @see Thread#join(long, int)
123	*/
124	public void timedJoin(Thread thread, long timeout)
125	throws InterruptedException {
126	if (timeout > 0) {
127	long ms = MILLISECONDS.convert(timeout, this);
128	int ns = excessNanos(timeout, ms);
129	thread.join(ms, ns);
130	}
131	}
132
133	/**
134	* Perform a <tt>Thread.sleep</tt> using the current time unit.
135	* This is a convenience method that converts time arguments into the
136	* form required by the <tt>Thread.sleep</tt> method.
137	* @param timeout the minimum time to sleep
138	* @throws InterruptedException if interrupted while sleeping.
139	* @see Thread#sleep
140	*/
141	public void sleep(long timeout) throws InterruptedException {
142	if (timeout > 0) {
143	long ms = MILLISECONDS.convert(timeout, this);
144	int ns = excessNanos(timeout, ms);
145	Thread.sleep(ms, ns);
146	}
147	}
148
149	/**
150	* Return the common name for this unit.
151	*/
152	public String toString() {
153	return unitName;
154	}
155
156	private final String unitName;
157
158	/* ordered indices for each time unit */
159	private static final int NS = 0;
160	private static final int US = 1;
161	private static final int MS = 2;
162	private static final int S = 3;
163
164	/** quick lookup table for conversion factors */
165	static final int[] multipliers = { 1,
166	1000,
167	1000*1000,
168	100010001000 };
169
170	/** lookup table to check saturation */
171	static final long[] overflows = {
172	// Note that because we are dividing these down anyway,
173	// we don't have to deal with asymmetry of MIN/MAX values.
174	0, // unused
175	Long.MAX_VALUE / 1000,
176	Long.MAX_VALUE / (1000 * 1000),
177	Long.MAX_VALUE / (1000 * 1000 * 1000) };
178
179	/** the index of this unit */
180	int index;
181
182	/** private constructor */
183	TimeUnit(int index, String name) {
184	this.index = index;
185	this.unitName = name;
186	}
187
188	/**
189	* Utility method to compute the excess-nanosecond argument to
190	* wait, sleep, join. The results may overflow, so public methods
191	* invoking this should document possible overflow unless
192	* overflow is known not to be possible for the given arguments.
193	*/
194	private int excessNanos(long time, long ms) {
195	if (index == NS)
196	return (int) (time - (ms * multipliers[MS-NS]));
197	else if (index == US)
198	return (int) ((time * multipliers[US-NS]) - (ms * multipliers[MS-NS]));
199	else
200	return 0;
201	}
202
203	/** Unit for one-second granularities. */
204	public static final TimeUnit SECONDS = new TimeUnit(S, "seconds");
205
206	/** Unit for one-millisecond granularities. */
207	public static final TimeUnit MILLISECONDS = new TimeUnit(MS, "milliseconds");
208
209	/** Unit for one-microsecond granularities. */
210	public static final TimeUnit MICROSECONDS = new TimeUnit(US, "microseconds");
211
212	/** Unit for one-nanosecond granularities. */
213	public static final TimeUnit NANOSECONDS = new TimeUnit(NS, "nanoseconds");
214
215	}