TimeUnit枚举类
TimeUnit是 java.util.concurrent 中的一个枚举类。一般让线程进行睡眠时使用：
TimeUnit.MILLISECONDS.sleep(100);
比如上面一行代码表示让当前线程睡眠100毫秒。
相比Thread.sleep()方法的一个好处就是， TimeUnit可以设置时间单位，比如上面的毫秒级别，看下面源码，有7个选项，纳秒、微妙、毫秒、秒、分钟、小时、天。
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. A * <tt>TimeUnit</tt> 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 <tt>TimeUnit</tt> 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> 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 timeout * implementation 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 enum TimeUnit { NANOSECONDS { public long toNanos(long d) { return d; } public long toMicros(long d) { return d/(C1/C0); } public long toMillis(long d) { return d/(C2/C0); } public long toSeconds(long d) { return d/(C3/C0); } public long toMinutes(long d) { return d/(C4/C0); } public long toHours(long d) { return d/(C5/C0); } public long toDays(long d) { return d/(C6/C0); } public long convert(long d, TimeUnit u) { return u.toNanos(d); } int excessNanos(long d, long m) { return (int)(d - (m*C2)); } }, MICROSECONDS { public long toNanos(long d) { return x(d, C1/C0, MAX/(C1/C0)); } public long toMicros(long d) { return d; } public long toMillis(long d) { return d/(C2/C1); } public long toSeconds(long d) { return d/(C3/C1); } public long toMinutes(long d) { return d/(C4/C1); } public long toHours(long d) { return d/(C5/C1); } public long toDays(long d) { return d/(C6/C1); } public long convert(long d, TimeUnit u) { return u.toMicros(d); } int excessNanos(long d, long m) { return (int)((d*C1) - (m*C2)); } }, MILLISECONDS { public long toNanos(long d) { return x(d, C2/C0, MAX/(C2/C0)); } public long toMicros(long d) { return x(d, C2/C1, MAX/(C2/C1)); } public long toMillis(long d) { return d; } public long toSeconds(long d) { return d/(C3/C2); } public long toMinutes(long d) { return d/(C4/C2); } public long toHours(long d) { return d/(C5/C2); } public long toDays(long d) { return d/(C6/C2); } public long convert(long d, TimeUnit u) { return u.toMillis(d); } int excessNanos(long d, long m) { return 0; } }, SECONDS { public long toNanos(long d) { return x(d, C3/C0, MAX/(C3/C0)); } public long toMicros(long d) { return x(d, C3/C1, MAX/(C3/C1)); } public long toMillis(long d) { return x(d, C3/C2, MAX/(C3/C2)); } public long toSeconds(long d) { return d; } public long toMinutes(long d) { return d/(C4/C3); } public long toHours(long d) { return d/(C5/C3); } public long toDays(long d) { return d/(C6/C3); } public long convert(long d, TimeUnit u) { return u.toSeconds(d); } int excessNanos(long d, long m) { return 0; } }, MINUTES { public long toNanos(long d) { return x(d, C4/C0, MAX/(C4/C0)); } public long toMicros(long d) { return x(d, C4/C1, MAX/(C4/C1)); } public long toMillis(long d) { return x(d, C4/C2, MAX/(C4/C2)); } public long toSeconds(long d) { return x(d, C4/C3, MAX/(C4/C3)); } public long toMinutes(long d) { return d; } public long toHours(long d) { return d/(C5/C4); } public long toDays(long d) { return d/(C6/C4); } public long convert(long d, TimeUnit u) { return u.toMinutes(d); } int excessNanos(long d, long m) { return 0; } }, HOURS { public long toNanos(long d) { return x(d, C5/C0, MAX/(C5/C0)); } public long toMicros(long d) { return x(d, C5/C1, MAX/(C5/C1)); } public long toMillis(long d) { return x(d, C5/C2, MAX/(C5/C2)); } public long toSeconds(long d) { return x(d, C5/C3, MAX/(C5/C3)); } public long toMinutes(long d) { return x(d, C5/C4, MAX/(C5/C4)); } public long toHours(long d) { return d; } public long toDays(long d) { return d/(C6/C5); } public long convert(long d, TimeUnit u) { return u.toHours(d); } int excessNanos(long d, long m) { return 0; } }, DAYS { public long toNanos(long d) { return x(d, C6/C0, MAX/(C6/C0)); } public long toMicros(long d) { return x(d, C6/C1, MAX/(C6/C1)); } public long toMillis(long d) { return x(d, C6/C2, MAX/(C6/C2)); } public long toSeconds(long d) { return x(d, C6/C3, MAX/(C6/C3)); } public long toMinutes(long d) { return x(d, C6/C4, MAX/(C6/C4)); } public long toHours(long d) { return x(d, C6/C5, MAX/(C6/C5)); } public long toDays(long d) { return d; } public long convert(long d, TimeUnit u) { return u.toDays(d); } int excessNanos(long d, long m) { return 0; } }; // Handy constants for conversion methods static final long C0 = 1L; static final long C1 = C0 * 1000L; static final long C2 = C1 * 1000L; static final long C3 = C2 * 1000L; static final long C4 = C3 * 60L; static final long C5 = C4 * 60L; static final long C6 = C5 * 24L; static final long MAX = Long.MAX_VALUE; /** * Scale d by m, checking for overflow. * This has a short name to make above code more readable. */ static long x(long d, long m, long over) { if (d > over) return Long.MAX_VALUE; if (d < -over) return Long.MIN_VALUE; return d * m; } // To maintain full signature compatibility with 1.5, and to improve the // clarity of the generated javadoc (see 6287639: Abstract methods in // enum classes should not be listed as abstract), method convert // etc. are not declared abstract but otherwise act as abstract methods. /** * Convert the given time duration in the given unit to this * unit. Conversions from finer to coarser granularities * truncate, so lose precision. For example converting * <tt>999</tt> milliseconds to seconds results in * <tt>0</tt>. 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. * * <p>For example, to convert 10 minutes to milliseconds, use: * <tt>TimeUnit.MILLISECONDS.convert(10L, TimeUnit.MINUTES)</tt> * * @param sourceDuration the time duration in the given <tt>sourceUnit</tt> * @param sourceUnit the unit of the <tt>sourceDuration</tt> argument * @return the converted duration in this 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 sourceDuration, TimeUnit sourceUnit) { throw new AbstractMethodError(); } /** * 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. * @see #convert */ public long toNanos(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>MICROSECONDS.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. * @see #convert */ public long toMicros(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>MILLISECONDS.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. * @see #convert */ public long toMillis(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>SECONDS.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. * @see #convert */ public long toSeconds(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>MINUTES.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. * @see #convert * @since 1.6 */ public long toMinutes(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>HOURS.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. * @see #convert * @since 1.6 */ public long toHours(long duration) { throw new AbstractMethodError(); } /** * Equivalent to <tt>DAYS.convert(duration, this)</tt>. * @param duration the duration * @return the converted duration * @see #convert * @since 1.6 */ public long toDays(long duration) { throw new AbstractMethodError(); } /** * 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 */ abstract int excessNanos(long d, long m); /** * 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 <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> {@code * 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. 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 <tt>Thread.join</tt> 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 <tt>Thread.sleep</tt> 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); } } }
