Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/publicdomain/zero/1.0/ */ package java.util.concurrent; import java.time.Duration; import java.time.temporal.ChronoUnit; import java.util.Objects; /** * A {@code TimeUnit} 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. A * {@code TimeUnit} does not maintain time information, but only * helps organize and use time representations that may be maintained * separately across various contexts. A nanosecond is defined as one * thousandth of a microsecond, a microsecond as one thousandth of a * millisecond, a millisecond as one thousandth of a second, a minute * as sixty seconds, an hour as sixty minutes, and a day as twenty four * hours. * * <p>A {@code TimeUnit} is mainly used to inform time-based methods * how a given timing 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> {@code * Lock lock = ...; * if (lock.tryLock(50L, TimeUnit.MILLISECONDS)) ...}</pre> * * while this code will timeout in 50 seconds: * <pre> {@code * Lock lock = ...; * if (lock.tryLock(50L, TimeUnit.SECONDS)) ...}</pre> * * Note however, that there is no guarantee that a particular timeout * implementation will be able to notice the passage of time at the * same granularity as the given {@code TimeUnit}. * * @since 1.5 * @author Doug Lea */ public enum TimeUnit { /** * Time unit representing one thousandth of a microsecond. */ NANOSECONDS(TimeUnit.NANO_SCALE), /** * Time unit representing one thousandth of a millisecond. */ MICROSECONDS(TimeUnit.MICRO_SCALE), /** * Time unit representing one thousandth of a second. */ MILLISECONDS(TimeUnit.MILLI_SCALE), /** * Time unit representing one second. */ SECONDS(TimeUnit.SECOND_SCALE), /** * Time unit representing sixty seconds. * @since 1.6 */ MINUTES(TimeUnit.MINUTE_SCALE), /** * Time unit representing sixty minutes. * @since 1.6 */ HOURS(TimeUnit.HOUR_SCALE), /** * Time unit representing twenty four hours. * @since 1.6 */ DAYS(TimeUnit.DAY_SCALE); // Scales as constants private static final long NANO_SCALE = 1L; private static final long MICRO_SCALE = 1000L * NANO_SCALE; private static final long MILLI_SCALE = 1000L * MICRO_SCALE; private static final long SECOND_SCALE = 1000L * MILLI_SCALE; private static final long MINUTE_SCALE = 60L * SECOND_SCALE; private static final long HOUR_SCALE = 60L * MINUTE_SCALE; private static final long DAY_SCALE = 24L * HOUR_SCALE; /* * Instances cache conversion ratios and saturation cutoffs for * the units up through SECONDS. Other cases compute them, in * method cvt. */ private final long scale; private final long maxNanos; private final long maxMicros; private final long maxMillis; private final long maxSecs; private final long microRatio; private final int milliRatio; // fits in 32 bits private final int secRatio; // fits in 32 bits private TimeUnit(long s) { this.scale = s; this.maxNanos = Long.MAX_VALUE / s; long ur = (s >= MICRO_SCALE) ? (s / MICRO_SCALE) : (MICRO_SCALE / s); this.microRatio = ur; this.maxMicros = Long.MAX_VALUE / ur; long mr = (s >= MILLI_SCALE) ? (s / MILLI_SCALE) : (MILLI_SCALE / s); this.milliRatio = (int) mr; this.maxMillis = Long.MAX_VALUE / mr; long sr = (s >= SECOND_SCALE) ? (s / SECOND_SCALE) : (SECOND_SCALE / s); this.secRatio = (int) sr; this.maxSecs = Long.MAX_VALUE / sr; } /** * General conversion utility. * * @param d duration * @param dst result unit scale * @param src source unit scale */ private static long cvt(long d, long dst, long src) { long r, m; if (src == dst) return d; else if (src < dst) return d / (dst / src); else if (d > (m = Long.MAX_VALUE / (r = src / dst))) return Long.MAX_VALUE; else if (d < -m) return Long.MIN_VALUE; else return d * r; } /** * Converts the given time duration in the given unit to this unit. * Conversions from finer to coarser granularities truncate, so * lose precision. For example, converting {@code 999} milliseconds * to seconds results in {@code 0}. Conversions from coarser to * finer granularities with arguments that would numerically * overflow saturate to {@code Long.MIN_VALUE} if negative or * {@code Long.MAX_VALUE} if positive. * * <p>For example, to convert 10 minutes to milliseconds, use: * {@code TimeUnit.MILLISECONDS.convert(10L, TimeUnit.MINUTES)} * * @param sourceDuration the time duration in the given {@code sourceUnit} * @param sourceUnit the unit of the {@code sourceDuration} argument * @return the converted duration in this unit, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. */ public long convert(long sourceDuration, TimeUnit sourceUnit) { switch (this) { case NANOSECONDS: return sourceUnit.toNanos(sourceDuration); case MICROSECONDS: return sourceUnit.toMicros(sourceDuration); case MILLISECONDS: return sourceUnit.toMillis(sourceDuration); case SECONDS: return sourceUnit.toSeconds(sourceDuration); default: return cvt(sourceDuration, scale, sourceUnit.scale); } } /** * Converts the given time duration to this unit. * * <p>For any TimeUnit {@code unit}, * {@code unit.convert(Duration.ofNanos(n))} * is equivalent to * {@code unit.convert(n, NANOSECONDS)}, and * {@code unit.convert(Duration.of(n, unit.toChronoUnit()))} * is equivalent to {@code n} (in the absence of overflow). * * @apiNote * This method differs from {@link Duration#toNanos()} in that it * does not throw {@link ArithmeticException} on numeric overflow. * * @param duration the time duration * @return the converted duration in this unit, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. * @throws NullPointerException if {@code duration} is null * @see Duration#of(long,TemporalUnit) * @since 11 */ public long convert(Duration duration) { long secs = duration.getSeconds(); int nano = duration.getNano(); if (secs < 0 && nano > 0) { // use representation compatible with integer division secs++; nano -= (int) SECOND_SCALE; } final long s, nanoVal; // Optimize for the common case - NANOSECONDS without overflow if (this == NANOSECONDS) nanoVal = nano; else if ((s = scale) < SECOND_SCALE) nanoVal = nano / s; else if (this == SECONDS) return secs; else return secs / secRatio; long val = secs * secRatio + nanoVal; return ((secs < maxSecs && secs > -maxSecs) || (secs == maxSecs && val > 0) || (secs == -maxSecs && val < 0)) ? val : (secs > 0) ? Long.MAX_VALUE : Long.MIN_VALUE; } /** * Equivalent to * {@link #convert(long, TimeUnit) NANOSECONDS.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. */ public long toNanos(long duration) { long s, m; if ((s = scale) == NANO_SCALE) return duration; else if (duration > (m = maxNanos)) return Long.MAX_VALUE; else if (duration < -m) return Long.MIN_VALUE; else return duration * s; } /** * Equivalent to * {@link #convert(long, TimeUnit) MICROSECONDS.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. */ public long toMicros(long duration) { long s, m; if ((s = scale) <= MICRO_SCALE) return (s == MICRO_SCALE) ? duration : duration / microRatio; else if (duration > (m = maxMicros)) return Long.MAX_VALUE; else if (duration < -m) return Long.MIN_VALUE; else return duration * microRatio; } /** * Equivalent to * {@link #convert(long, TimeUnit) MILLISECONDS.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. */ public long toMillis(long duration) { long s, m; if ((s = scale) <= MILLI_SCALE) return (s == MILLI_SCALE) ? duration : duration / milliRatio; else if (duration > (m = maxMillis)) return Long.MAX_VALUE; else if (duration < -m) return Long.MIN_VALUE; else return duration * milliRatio; } /** * Equivalent to * {@link #convert(long, TimeUnit) SECONDS.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. */ public long toSeconds(long duration) { long s, m; if ((s = scale) <= SECOND_SCALE) return (s == SECOND_SCALE) ? duration : duration / secRatio; else if (duration > (m = maxSecs)) return Long.MAX_VALUE; else if (duration < -m) return Long.MIN_VALUE; else return duration * secRatio; } /** * Equivalent to * {@link #convert(long, TimeUnit) MINUTES.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. * @since 1.6 */ public long toMinutes(long duration) { return cvt(duration, MINUTE_SCALE, scale); } /** * Equivalent to * {@link #convert(long, TimeUnit) HOURS.convert(duration, this)}. * @param duration the duration * @return the converted duration, * or {@code Long.MIN_VALUE} if conversion would negatively overflow, * or {@code Long.MAX_VALUE} if it would positively overflow. * @since 1.6 */ public long toHours(long duration) { return cvt(duration, HOUR_SCALE, scale); } /** * Equivalent to * {@link #convert(long, TimeUnit) DAYS.convert(duration, this)}. * @param duration the duration * @return the converted duration * @since 1.6 */ public long toDays(long duration) { return cvt(duration, DAY_SCALE, scale); } /** * Utility to compute the excess-nanosecond argument to wait, * sleep, join. * @param d the duration * @param m the number of milliseconds * @return the number of nanoseconds */ private int excessNanos(long d, long m) { long s; if ((s = scale) == NANO_SCALE) return (int) (d - (m * MILLI_SCALE)); else if (s == MICRO_SCALE) return (int) ((d * 1000L) - (m * MILLI_SCALE)); else return 0; } /** * Performs a timed {@link Object#wait(long, int) Object.wait} * using this time unit. * This is a convenience method that converts timeout arguments * into the form required by the {@code Object.wait} method. * * <p>For example, you could implement a blocking {@code poll} method * (see {@link BlockingQueue#poll(long, TimeUnit) BlockingQueue.poll}) * using: * * <pre> {@code * public E poll(long timeout, TimeUnit unit) * throws InterruptedException { * synchronized (lock) { * while (isEmpty()) { * unit.timedWait(lock, timeout); * ... * } * } * }}</pre> * * @param obj the object to wait on * @param timeout the maximum time to wait. If less than * or equal to zero, do not wait at all. * @throws InterruptedException if interrupted while waiting */ public void timedWait(Object obj, long timeout) throws InterruptedException { if (timeout > 0) { long ms = toMillis(timeout); int ns = excessNanos(timeout, ms); obj.wait(ms, ns); } } /** * Performs a timed {@link Thread#join(long, int) Thread.join} * using this time unit. * This is a convenience method that converts time arguments into the * form required by the {@code Thread.join} method. * * @param thread the thread to wait for * @param timeout the maximum time to wait. If less than * or equal to zero, do not wait at all. * @throws InterruptedException if interrupted while waiting */ public void timedJoin(Thread thread, long timeout) throws InterruptedException { if (timeout > 0) { long ms = toMillis(timeout); int ns = excessNanos(timeout, ms); thread.join(ms, ns); } } /** * Performs a {@link Thread#sleep(long, int) Thread.sleep} using * this time unit. * This is a convenience method that converts time arguments into the * form required by the {@code Thread.sleep} method. * * @param timeout the minimum time to sleep. If less than * or equal to zero, do not sleep at all. * @throws InterruptedException if interrupted while sleeping */ public void sleep(long timeout) throws InterruptedException { if (timeout > 0) { long ms = toMillis(timeout); int ns = excessNanos(timeout, ms); Thread.sleep(ms, ns); } } /** * Converts this {@code TimeUnit} to the equivalent {@code ChronoUnit}. * * @return the converted equivalent ChronoUnit * @since 9 */ public ChronoUnit toChronoUnit() { switch (this) { case NANOSECONDS: return ChronoUnit.NANOS; case MICROSECONDS: return ChronoUnit.MICROS; case MILLISECONDS: return ChronoUnit.MILLIS; case SECONDS: return ChronoUnit.SECONDS; case MINUTES: return ChronoUnit.MINUTES; case HOURS: return ChronoUnit.HOURS; case DAYS: return ChronoUnit.DAYS; default: throw new AssertionError(); } } /** * Converts a {@code ChronoUnit} to the equivalent {@code TimeUnit}. * * @param chronoUnit the ChronoUnit to convert * @return the converted equivalent TimeUnit * @throws IllegalArgumentException if {@code chronoUnit} has no * equivalent TimeUnit * @throws NullPointerException if {@code chronoUnit} is null * @since 9 */ public static TimeUnit of(ChronoUnit chronoUnit) { switch (Objects.requireNonNull(chronoUnit, "chronoUnit")) { case NANOS: return TimeUnit.NANOSECONDS; case MICROS: return TimeUnit.MICROSECONDS; case MILLIS: return TimeUnit.MILLISECONDS; case SECONDS: return TimeUnit.SECONDS; case MINUTES: return TimeUnit.MINUTES; case HOURS: return TimeUnit.HOURS; case DAYS: return TimeUnit.DAYS; default: throw new IllegalArgumentException("No TimeUnit equivalent for " + chronoUnit); } } }