public class Counter implements Comparable<Counter> {
    private volatile long value;

    public long getValue() {
        return value;
    }

    public synchronized void reset() {
        value = 0;
        notifyAll();
    }

    public synchronized void incr() {
        value++;
        notifyAll();
    }

    public synchronized void decr() {
        value--;
        notifyAll();
    }

    @Override
    public int hashCode() {
        return 17 + (int) (this.value ^ (this.value >>> 32));
    }

    @Override
    public boolean equals(Object o) {
        return o instanceof Counter && ((Counter)o).value == value;
    }

    @Override
    public int compareTo(Counter o) {
        if( o.value > value )
            return -1;
        else if( o.value < value )
            return 1;
        else
            return 0;
    }
}