Question

Design and implement the class Day that implements the day of the week in a program. The class Day should store the day, such as Sun for Sunday. The program should be able to perform the following operations on an object of type Day:

1. Set the day.
2. Print the day.
3. Return the day.
4. Return the next day.
5. Return the previous day.
6. Calculate and return the day by adding certain days to the current day. For example, if the current day is Monday and we add 4 days, the day to be returned is Friday. Similarly, if today is Tuesday and we add 13 days, the day to be returned is Monday.
7. Add the appropriate constructors.
8. Write the definitions of the methods to implement the operations for the class Day, as defined in A through G.
1. Write a program to test various operations on the class Day.

Answer 1

Thanks for the question, here is the class Day and DayTest. Have implemented both the classes in Java as the programming language was not explicitly mentioned.

The DayTest contains the test of various operations.

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public class Day {


    private String day;

// below are the only valid names for a day
    private static final String SHORT_NAMES[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};


    public Day(String day) {
        setDay(day);
    }

    // a.
    private void setDay(String day) {

        boolean validArgument = false;
        for (String name : SHORT_NAMES) {
            if (day.equals(name)) {
                this.day = day;
                validArgument = true;
                break;
            }
        }

// if the day name is not a valid name throw error
        if (!validArgument)
            throw new IllegalArgumentException("Invalid day name entered");
    }

    // b.
    public void printDay() {
        System.out.println(day + "day");
    }

    // c.
    public String getDay() {
        return day;
    }

    // d. Return the next day.

    public String nextDay() {
        int nextDay = 0;
        for (int i = 0; i < SHORT_NAMES.length; i++) {
            if (SHORT_NAMES[i].equals(day)) {
                nextDay = (i + 1) % 7;
                break;
            }
        }
        return SHORT_NAMES[nextDay] + "day";
    }

    // e.
    public String previousDay() {
        int previousDay = 0;
        for (int i = 0; i < SHORT_NAMES.length; i++) {
            if (SHORT_NAMES[i].equals(day)) {
                previousDay = i - 1 == -1 ? 6 : i - 1;
                break;
            }
        }
        return SHORT_NAMES[previousDay] + "day";
    }

    // f.
    public String dayAfterNDays(int n) {

        int index = 0;
        for (int i = 0; i < SHORT_NAMES.length; i++) {
            if (SHORT_NAMES[i].equals(day)) {
                index = i;
                break;
            }
        }
        int indexOfNthDay = (index + n) % 7;
        if (indexOfNthDay < 0) indexOfNthDay = 7 + indexOfNthDay;
        return SHORT_NAMES[indexOfNthDay] + "day";

    }

}

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public class DayTest {


    public static void main(String[] args) {

        Day today = new Day("Mon");
        System.out.print("Today is : ");today.printDay();
        System.out.println("Next day: " + today.nextDay());
        System.out.println("Next day: " + today.previousDay());
        System.out.println("After 4 days : " + today.dayAfterNDays(4));
        System.out.println("After 13 days : " + today.dayAfterNDays(13));
        System.out.println("Previous -14 days : " + today.dayAfterNDays(-14));


    }
}

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thanks a lot. Please do up vote please : )