Question

QUESTION:

Modify the TimeSpan class from Chapter 8 to include a compareTo method that compares time spans by their length. A time span that represents a shorter amount of time is considered to be “less than” one that represents a longer amount of time. For example, a span of 3 hours and 15 minutes is greater than a span of 1 hour and 40 minutes.

GIVEN TIMESPAN FILE

/*
* Adapted for CS211 from Building Java Programs, 4th Edition,
* by Stuart Reges and Marty Stepp
* adapted by James Livingston, Bellevue College Adjunct Instructor
*/
// Represents a time span of elapsed hours and minutes.
// Simple implementation using only total minutes as state.
public class TimeSpan {
private int totalMinutes;

// Constructs a time span with the given interval.
// pre: hours >= 0 && minutes >= 0
public TimeSpan(int hours, int minutes) {
totalMinutes = 0;
add(hours, minutes);
}

// Adds the given interval to this time span.
// pre: hours >= 0 && minutes >= 0
public void add(int hours, int minutes) {
totalMinutes += 60 * hours + minutes;
}

// Returns a String for this time span such as "6h15m".
public String toString() {
return (totalMinutes / 60) + "h"
+ (totalMinutes % 60) + "m";
}
}

GIVEN TIMESPANMAIN FILE

/*
* TimeSpanClient: a simple test client for the TimeSpan class
* Shows creation of an instance object, displaying that object,
* adding hours and minutes to that object, and showing the result.
*/
public class TimeSpanClient {
public static void main(String[] args) {
int h1 = 13, m1 = 30;
TimeSpan t1 = new TimeSpan(h1, m1);
System.out.println("New object t1: " + t1);
  
h1 = 3; m1 = 40;
System.out.println("Adding " + h1 + " hours, " + m1 + " minutes to t1");
t1.add(h1, m1);
System.out.println("New t1 state: " + t1);
}
}

Answer 1

Here is the modified code for TimeSpan.java and TimeSpanClient.java. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// TimeSpan.java

//implemented Comparable interface, which has the compareTo method

//and can be used to sort a list or array of TimeSpan objects without

//using a Comparator

public class TimeSpan implements Comparable<TimeSpan> {

    private int totalMinutes;

    // Constructs a time span with the given interval.

    // pre: hours >= 0 && minutes >= 0

    public TimeSpan(int hours, int minutes) {

         totalMinutes = 0;

         add(hours, minutes);

    }

    // Adds the given interval to this time span.

    // pre: hours >= 0 && minutes >= 0

    public void add(int hours, int minutes) {

         totalMinutes += 60 * hours + minutes;

    }

    // Returns a String for this time span such as "6h15m".

    public String toString() {

         return (totalMinutes / 60) + "h" + (totalMinutes % 60) + "m";

    }

    // method to compare this time span with other

    // returns a negative value if this time span is shorter than other

    // returns 0 if both have same duration

    // returns a positive value if this time span is longer than other

    public int compareTo(TimeSpan other) {

         if (this.totalMinutes < other.totalMinutes) {

             return -1; // this < other

         } else if (this.totalMinutes > other.totalMinutes) {

             return 1; // this > other

         } else {

             return 0; // this = other

         }

    }

}

// TimeSpanClient.java

public class TimeSpanClient {

    public static void main(String[] args) {

         int h1 = 13, m1 = 30;

         TimeSpan t1 = new TimeSpan(h1, m1);

         System.out.println("New object t1: " + t1);

         h1 = 3;

         m1 = 40;

         System.out.println("Adding " + h1 + " hours, " + m1 + " minutes to t1");

         t1.add(h1, m1);

         System.out.println("New t1 state: " + t1);

         // creating another TimeSpan object, testing compareTo method using the

         // two objects

         TimeSpan t2 = new TimeSpan(10, 20);

         System.out.println("New object t2: " + t2);

         System.out.println("t1.compareTo(t2): " + t1.compareTo(t2));

         System.out.println("t2.compareTo(t1): " + t2.compareTo(t1));

         System.out.println("t1.compareTo(t1): " + t1.compareTo(t1));

    }

}

/*OUTPUT*/

New object t1: 13h30m

Adding 3 hours, 40 minutes to t1

New t1 state: 17h10m

New object t2: 10h20m

t1.compareTo(t2): 1

t2.compareTo(t1): -1

t1.compareTo(t1): 0