@Test
public void whenGaurdConditionIsTrue_IsSuccessful() {
    Monitor monitor = new Monitor();
    boolean enteredInCriticalSection = false;

    Monitor.Guard gaurdCondition = monitor.newGuard(this::returnTrue);

    if (monitor.enterIf(gaurdCondition)) {
        try {
            System.out.println("Entered in critical section");
            enteredInCriticalSection = true;
        } finally {
            monitor.leave();
        }
    }

    Assert.assertTrue(enteredInCriticalSection);

}
 

@Test
public void whenGaurdConditionIsFalse_IsSuccessful() {
    Monitor monitor = new Monitor();
    boolean enteredInCriticalSection = false;

    Monitor.Guard gaurdCondition = monitor.newGuard(this::returnFalse);

    if (monitor.enterIf(gaurdCondition)) {
        try {
            System.out.println("Entered in critical section");
            enteredInCriticalSection = true;
        } finally {
            monitor.leave();
        }
    }

    Assert.assertFalse(enteredInCriticalSection);
}
 

public void addToCourse(String item) throws InterruptedException {
    Monitor.Guard studentsBelowCapacity = monitor.newGuard(this::isStudentsCapacityUptoLimit);
    monitor.enterWhen(studentsBelowCapacity);
    try {
        students.add(item);
    } finally {
        monitor.leave();
    }
}