// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =================================================================================================
package com.twitter.common.util;
/**
* An abstraction of the system clock.
*
* @author John Sirois
*/
public interface Clock {
/**
* A clock that returns the the actual time reported by the system.
*/
Clock SYSTEM_CLOCK = new Clock() {
@Override public long nowMillis() {
return System.currentTimeMillis();
}
@Override public long nowNanos() {
return System.nanoTime();
}
@Override public void waitFor(long millis) throws InterruptedException {
Thread.sleep(millis);
}
};
/**
* Returns the current time in milliseconds since the epoch.
*
* @return The current time in milliseconds since the epoch.
* @see System#currentTimeMillis()
*/
long nowMillis();
/**
* Returns the current time in nanoseconds. Should be used only for relative timing.
* {@see System.nanoTime()} for tips on using the value returned here.
*
* @return A measure of the current time in nanoseconds.
*/
long nowNanos();
/**
* Waits for the given amount of time to pass on this clock before returning.
*
* @param millis the amount of time to wait in milliseconds
* @throws InterruptedException if this wait was interrupted
*/
void waitFor(long millis) throws InterruptedException;
}