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. * *
A TimeUnit 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: *
Lock lock = ...; * if ( lock.tryLock(50L, TimeUnit.MILLISECONDS) ) ... ** while this code will timeout in 50 seconds: *
* Lock lock = ...; * if ( lock.tryLock(50L, TimeUnit.SECONDS) ) ... ** * 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 TimeUnit. * * @since 1.5 * @author Doug Lea */ public final class TimeUnit implements java.io.Serializable { /* 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 */ private static final int[] multipliers = { 1, 1000, 1000*1000, 1000*1000*1000 }; /** lookup table to check saturation */ private 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 */ private int index; /** Common name for unit */ private final String unitName; /** private constructor */ TimeUnit(int index, String name) { this.index = index; this.unitName = name; } /** 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"); /** * Utility method to compute the excess-nanosecond argument to * wait, sleep, join. */ 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; } /** * Perform conversion based on given delta representing the * difference between units * @param delta the difference in index values of source and target units * @param duration the duration * @return converted duration or saturated value */ private static long doConvert(int delta, long duration) { if (delta == 0) return duration; if (delta < 0) return duration / multipliers[-delta]; if (duration > overflows[delta]) return Long.MAX_VALUE; if (duration < -overflows[delta]) return Long.MIN_VALUE; return duration * multipliers[delta]; } /** * 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 * 999 milliseconds to seconds results in * 0. Conversions from coarser to finer granularities * with arguments that would numerically overflow saturate to * Long.MIN_VALUE if negative or Long.MAX_VALUE * if positive. * * @param duration the time duration in the given unit * @param unit the unit of the duration argument * @return the converted duration in this unit, * or Long.MIN_VALUE if conversion would negatively * overflow, or Long.MAX_VALUE if it would positively overflow. */ public long convert(long duration, TimeUnit unit) { return doConvert(unit.index - index, duration); } /** * Equivalent to NANOSECONDS.convert(duration, this). * @param duration the duration * @return the converted duration, * or Long.MIN_VALUE if conversion would negatively * overflow, or Long.MAX_VALUE if it would positively overflow. * @see #convert */ public long toNanos(long duration) { return doConvert(index, duration); } /** * Equivalent to MICROSECONDS.convert(duration, this). * @param duration the duration * @return the converted duration, * or Long.MIN_VALUE if conversion would negatively * overflow, or Long.MAX_VALUE if it would positively overflow. * @see #convert */ public long toMicros(long duration) { return doConvert(index - US, duration); } /** * Equivalent to MILLISECONDS.convert(duration, this). * @param duration the duration * @return the converted duration, * or Long.MIN_VALUE if conversion would negatively * overflow, or Long.MAX_VALUE if it would positively overflow. * @see #convert */ public long toMillis(long duration) { return doConvert(index - MS, duration); } /** * Equivalent to SECONDS.convert(duration, this). * @param duration the duration * @return the converted duration. * @see #convert */ public long toSeconds(long duration) { return doConvert(index - S, duration); } /** * Perform a timed Object.wait using this time unit. * This is a convenience method that converts timeout arguments into the * form required by the Object.wait method. *
For example, you could implement a blocking poll method (see * {@link BlockingQueue#poll BlockingQueue.poll} using: *
public synchronized Object poll(long timeout, TimeUnit unit) throws InterruptedException {
* while (empty) {
* unit.timedWait(this, timeout);
* ...
* }
* }
* @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 = toMillis(timeout);
int ns = excessNanos(timeout, ms);
obj.wait(ms, ns);
}
}
/**
* Perform a timed Thread.join using this time unit.
* This is a convenience method that converts time arguments into the
* form required by the Thread.join 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 = toMillis(timeout);
int ns = excessNanos(timeout, ms);
thread.join(ms, ns);
}
}
/**
* Perform a Thread.sleep using this unit.
* This is a convenience method that converts time arguments into the
* form required by the Thread.sleep 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 = toMillis(timeout);
int ns = excessNanos(timeout, ms);
Thread.sleep(ms, ns);
}
}
/**
* Return the common name for this unit.
*/
public String toString() {
return unitName;
}
/**
* Resolves instances being deserialized to a single instance per
* unit.
*/
private Object readResolve() {
switch(index) {
case NS: return NANOSECONDS;
case US: return MICROSECONDS;
case MS: return MILLISECONDS;
case S: return SECONDS;
default: assert(false); return null;
}
}
}