Java class that performs an operation after a predetermined number of actions occur.

CountDown.java

import java.util.concurrent.atomic.AtomicInteger;

/**
 * Performs an operation after a predetermined number of actions occur.
 */
abstract public class CountDown {

    private AtomicInteger count;

    /**
     * Create a new instance that will fire its onReady after count calls to countDown()
     * @param count The number of countDown() call required
     */
    public CountDown(int count) {
        this.count = new AtomicInteger(count);
    }

    /**
     * @return Number of remaining calls to countDown() required
     */
    public int get() {
        return count.get();
    }

    /**
     * Reduce the count of the internal counter by one and call onReady if the counter reaches zero.
     */
    public void countDown() {
        int current = count.decrementAndGet();
        if (current == 0) {
            onReady();
        }
    }

    /**
     * Method to call when the internal counter reaches zero.
     */
    abstract protected void onReady();

}