import java.util.concurrent.locks.*; import java.util.ArrayList; public class SaksMonitor { private Lock laas = new ReentrantLock(); private ArrayList sakser = new ArrayList<>(); public void settInn(Saks saks) { laas.lock(); try { sakser.add(saks); } finally { laas.unlock(); } } public int antallSakser() { laas.lock(); try { return sakser.size(); } finally { laas.unlock(); } } }