Package org.apache.hadoop.util

Class Time

java.lang.Object

org.apache.hadoop.util.Time

@LimitedPrivate({"HDFS","MapReduce"})
@Unstable
public final class Time
extends java.lang.Object

Utility methods for getting the time and computing intervals.

Constructor Summary

Constructors

Constructor	Description
Time()

Method Summary

Modifier and Type	Method	Description
static java.lang.String	formatTime(long millis)	Convert time in millisecond to human readable format.
static long	getUtcTime()	Get the current UTC time in milliseconds.
static long	monotonicNow()	Current time from some arbitrary time base in the past, counting in milliseconds, and not affected by settimeofday or similar system clock changes.
static long	monotonicNowNanos()	Same as monotonicNow() but returns its result in nanoseconds.
static long	now()	Current system time.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Time

public Time()

Method Detail

now

public static long now()

Current system time. Do not use this to calculate a duration or interval to sleep, because it will be broken by settimeofday. Instead, use monotonicNow.

Returns:

current time in msec.

monotonicNow

public static long monotonicNow()

Current time from some arbitrary time base in the past, counting in milliseconds, and not affected by settimeofday or similar system clock changes. This is appropriate to use when computing how much longer to wait for an interval to expire. This function can return a negative value and it must be handled correctly by callers. See the documentation of System#nanoTime for caveats.

Returns:

a monotonic clock that counts in milliseconds.

monotonicNowNanos

public static long monotonicNowNanos()

Same as monotonicNow() but returns its result in nanoseconds. Note that this is subject to the same resolution constraints as System.nanoTime().

Returns:

a monotonic clock that counts in nanoseconds.

formatTime

public static java.lang.String formatTime(long millis)

Convert time in millisecond to human readable format.

Parameters:

millis - millisecond.

Returns:

a human readable string for the input time

getUtcTime

public static long getUtcTime()

Get the current UTC time in milliseconds.

Returns:

the current UTC time in milliseconds.