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 lock, in this * case, 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 { /** * Perform the conversion based on given index 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 the * current unit. Conversions from finer to coarser granulaties * 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 the current 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 the current 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 = MILLISECONDS.convert(timeout, this);
int ns = excessNanos(timeout, ms);
obj.wait(ms, ns);
}
}
/**
* Perform a timed Thread.join using the current 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 = MILLISECONDS.convert(timeout, this);
int ns = excessNanos(timeout, ms);
thread.join(ms, ns);
}
}
/**
* Perform a Thread.sleep using the current time 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 = 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;
}
/**
* Returns true if the given object is a TimeUnit representing
* the same unit as this TimeUnit.
* @param x the object to compare
* @return true if equal
*/
public boolean equals(Object x) {
if (!(x instanceof TimeUnit))
return false;
return ((TimeUnit)x).index == index;
}
/**
* Returns a hash code for this TimeUnit.
* @return the hash code
*/
public int hashCode() {
return unitName.hashCode();
}
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");
}