実行頻度リミッター

Throttle.java

public class Throttle {
	protected final int maxHistorySize = 10;
	protected final double timeEpsilon = 1d/(1000 * 1000);
	
	protected double maxThrottlePerSec = 1d;
	
	protected LinkedList<Double> history = new LinkedList<>(); 
	
	public Throttle(double maxThrottle){
		this.maxThrottlePerSec = maxThrottle;
	}
	
	public void waitLimit(){
		synchronized(history){
			double interval = planNextInterval();
			if (interval >= timeEpsilon){
				try {
					long millis = (long)(interval*1000);
					int nanos = (int)(interval*1000*1000*1000 - Math.floor(interval*1000)*1000*1000);
					Thread.sleep(millis, nanos);
				} catch (InterruptedException e) {
					// do nothing
				}
			}
			history.addLast(getCurrentTime());
			while(history.size() > maxHistorySize)
				history.removeFirst();
		}
	}
	
	public double measureThroughput(){
		synchronized(history){
			if (history.size()<2) return 0d;
			double sampleDuration = history.getLast() - history.getFirst();
			int sampleSize = history.size()-1;
			return sampleSize / sampleDuration;
		}
	}
	
	protected static double getCurrentTime(){
		return System.currentTimeMillis() * 0.001;
	}

	protected double planNextInterval(){
		if (maxThrottlePerSec <= 0) return 0d;
		
		double targetInterval = 1d/maxThrottlePerSec;
		double currentTime = getCurrentTime();
		
		if (!history.isEmpty()){
			double lastTime = history.getLast();
			return Math.max(targetInterval-(currentTime-lastTime), 0d);
		} else {
			return targetInterval;
		}
	}
	
	public static void main(String[] args){
		double maxThrottle = Double.parseDouble(args[0]);
		Throttle thr = new Throttle(maxThrottle);
		while(true){
			thr.waitLimit();
			System.out.println(thr.measureThroughput());
		}
	}
}

Throttle throttle = new Throttle(100);

while(true){

  // do something ...

  throttle.waitLimit();
}

のようにすると、だいたい秒間100回くらいに調整される。("do something" 部分で平均0.01秒以上かかる場合は100回未満になるかもしれない。)