class Glass {

        int capacity = 0;

        void add(int value) {
            System.out.println("Było " + capacity);
            System.out.println("Dodaj " + value);
            capacity += value;
            System.out.println("Teraz jest " + capacity);
        }

        void subtract(int value) {
            System.out.println("Było " + capacity);
            System.out.println("Odejmij " + value);
            capacity -= value;
            System.out.println("Teraz jest " + capacity);
        }
    }