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JUnit Toolkit enhances JUnit with performance testing, asymptotic behaviour analysis, and concurrency testing.

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/*
 * Copyright The Sett Ltd, 2005 to 2014.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License 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.thesett.common.throttle;

/**
 * SleepThrottle is a Throttle implementation that generates short pauses using the thread sleep methods. As the pauses
 * get shorter, this technique gets more innacurate. In practice, around 100 Hz is the cap rate for accuracy.
 *
 * 
 * CRC Card Responsibilities  Collaborations
 * 
 Accept throttling rate in operations per second.
 * 
 Inject short pauses to fill out processing cycles to a specified rate.
 * 
 Check against a throttle speed without waiting.
 * 
 *
 * @author Rupert Smith
 */
public class SleepThrottle extends BaseThrottle implements Throttle
{
    /** Holds the time of the last call to the throttle method in nano seconds. */
    private long lastTimeNanos;

    /**
     * This method can only be called at the rate set by the {@link #setRate} method, if it is called faster than this
     * it will inject short pauses to restrict the call rate to that rate.
     *
     * @throws InterruptedException If interrupted whilst performing a blocking wait on the throttle.
     */
    public synchronized void throttle() throws InterruptedException
    {
        // Get the current time in nanos.
        long currentTimeNanos = System.nanoTime();

        // Don't introduce any pause on the first call.
        if (!firstCall)
        {
            // Check if there is any time left in the cycle since the last call to this method and introduce a short pause
            // to fill that time if there is.
            long remainingTimeNanos = cycleTimeNanos - (currentTimeNanos - lastTimeNanos);

            if (remainingTimeNanos > 0)
            {
                long milliPause = remainingTimeNanos / 1000000;
                int nanoPause = (int) (remainingTimeNanos % 1000000);

                Thread.sleep(milliPause, nanoPause);
            }
        }
        else
        {
            firstCall = false;
        }

        // Update the last time stamp.
        lastTimeNanos = System.nanoTime();
    }
}

Responsibilities	Collaborations *
Accept throttling rate in operations per second. *
Inject short pauses to fill out processing cycles to a specified rate. *
Check against a throttle speed without waiting. *