Question

Problem 1.(1) Implement a class Clock whose getHours and getMinutes methods return the current time at your location. (Call java.time.LocalTime.now().toString() or, if you are not using Java 8, new java.util.Date().toString() and extract the time from that string.) Also provide a getTime method that returns a string with the hours and minutes by calling the getHours and getMinutesmethods.

(2) Provide a subclass WorldClock whose constructor accepts a time offset. For example, if you live in California, a new WorldClock(3) should show the time in New York, three time zones ahead. Which methods did you override? (You should not override getTime.)

Skeleton Code Below

World Clock-

/**
* PART II.
* Provide a subclass of Clock namded WorldClock whose constructor
* accepts a time offset. For example, if you live in California,
* a new WorldClock(3) should show the time in New York, three
* time zones ahead. You should not override getTime.
*/
public class WorldClock extends Clock
{
// Your work goes here
. . .

}

Clock-

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
/**
Part I: Implement a class Clock whose getHours, getMinutes and
getTime methods return the current time at your location.
Return the time as a string.

There are two ways to retrieve the current time as a String:

1) Before Java 8 use new Date().toString()
2) With Java 8, you can use 3 classes in the java.time package:
Instant, LocalDateTime and ZoneId. Here's how you do it:
String timeString = LocalDateTime.ofInstant(Instant.now(),
ZoneId.systemDefault()).toString()

With either method, you'll need to extract the hours and
minutes as a substring.
*/
public class Clock
{
/**
* gets hours
* @return hours of current time in string
*/
public String getHours()
{
final int HOUR_START = 11;
return currentTime().substring(HOUR_START, HOUR_START + 2);
}

/**
* gets minutes
* @return hours of current time in string
*/
public String getMinutes()
{
final int MINUTE_START = 14;
return currentTime().substring(MINUTE_START, MINUTE_START + 2);
}

/**
* gets current time composed of hours and minutes
* @return time in string;
*/
public String getTime()
{
return getHours() + ":" + getMinutes();
}

/**
Returns the current Date and Time as a String.
*/
private String currentTime()
{
return LocalDateTime.ofInstant(Instant.now(),
ZoneId.systemDefault()).toString();
}
}

ClockDemo

/**
* Tests the Clock and WorldClock Classes.
*/
public class ClockDemo
{
public static void main(String[] args)
{
//test WorldClock
System.out.println("");
System.out.println("Testing WorldClock class");
int offset = 3;
System.out.println("Offset: " + offset);
WorldClock wclock = new WorldClock(offset);
System.out.println("Hours: " + wclock.getHours());
System.out.println("Minutes: " + wclock.getMinutes());
System.out.println("Time: " + wclock.getTime());
}
}

Answer 1

Answer;

// Clock.java

public class Clock {

                // private int hour, minute;

                public Clock() {

                                /*

                                * String s = new java.util.Date().toString(); hour =

                                * Integer.parseInt(s.substring(11, 13)); minute =

                                * Integer.parseInt(s.substring(14, 16));

                                */

                }

                /**

                * instead of assigning to a variable from constructor, it is much better

                * to return the current time whenever getMinute() or getHour() called,

                * which will always provide correct time

                */

                public int getMinute() {

                                String s = new java.util.Date().toString();

                                return Integer.parseInt(s.substring(14, 16));

                }

                public int getHour() {

                                String s = new java.util.Date().toString();

                                return Integer.parseInt(s.substring(11, 13));

                }

                /**

                * returns the current time in HH:MM format

                */

                public String getTime() {

                                return getHour() + ":" + getMinute();

                }

}

// WorldClock.java

public class WorldClock extends Clock {

                private int timeOffset;

                //constructor accepting an offset

                public WorldClock(int timeOffset) {

                                this.timeOffset = timeOffset;

                }

                @Override

                public int getHour() {

                                // adding offset value to hour

                                int hour = super.getHour() + timeOffset;

                                if (hour > 23) {

                                                /**

                                                * hour is now greater than 23 , so continuously subtracting from 23

                                                * to keep it under range

                                                */

                                                while (hour > 23) {

                                                                hour = 23 - hour;

                                                }

                                }

                                if (hour < 0) {

                                                /**

                                                * hour is now smaller than 0 [negative offset], so continuously

                                                * adding 23 to keep it under range

                                                */

                                                while (hour < 0) {

                                                                hour = 23 + hour;

                                                }

                                }

                                return hour;

                }

}

// Test.java (tester class with main method)

public class Test {

                public static void main(String[] args) {

                                Clock c = new Clock();

                                System.out.printf("%02d:%02d\n", c.getHour(), c.getMinute());

                                /**

                                * Testing the world clock class

                                */

                                WorldClock worldClock = new WorldClock(3);

                                /**

                                * displaying current time of worldClock object using getTime method

                                */

                                System.out.println(worldClock.getTime());

                }

}

/*OUTPUT*/

10:51

13:51