NewSwitchExample.java

private static int getDayExpense2(WeekDay day) {
        return switch (day) {
            case SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY -> 100;
//            case FRIDAY -> 200;  // without using 'default', this line creates compile error
//            case FRIDAY, SATURDAY -> 200  // valid
            default -> 200; // valid
        };
    }

    // We must use 'default' if we have int, String etc. common parameter type.
    // Because it can't determine which value is missing, so it expects a general fall-through => default.
    private static int getDayExpense3(int indexOfWeek) {
        return switch (indexOfWeek) {
            case 1, 2, 3, 4, 5 -> 100;
            default -> 200;
        };
    }

    // We can also do some extra work inside the case block. When returning value, we've to use 'yield' keyword.
    private static int getDayExpense4(WeekDay day) {
        return switch (day) {
            case SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY -> {
                var val = eatLunch();
                yield val;
            }

            case FRIDAY, SATURDAY -> {
                yield goToRestaurant();
            }
        };
    }

    private static int goToRestaurant() {
        return 200;
    }

    private static int eatLunch() {
        return 100;
    }