Throttle a particular action if it happens too often within a period of time

Throttle.java

package com.nowucca.util;

import com.nowucca.exception.InternalException;
import java.util.concurrent.atomic.AtomicInteger;

/**
 */
public class Throttle {

    private static int threshold;
    private long beginningOfWindow;
    private long windowSizeMillis;
    private AtomicInteger count;


    public Throttle(int threshold, long windowSizeMillis) {

        assert windowSizeMillis > 0;
        assert threshold > 0;

        this.threshold = threshold;
        this.windowSizeMillis = windowSizeMillis;
        this.count = new AtomicInteger(0);
    }

    public void throttle() throws ThrottledException, InternalException {

        long now = System.currentTimeMillis();
        if (now - beginningOfWindow > windowSizeMillis) {
            count.set(0);
            beginningOfWindow = now;
        }
        if (count.incrementAndGet() > threshold) {
            throw new ThrottledException();
        }
    }
}