Chapter 10, Problem 10.1PE

(The Time class) Design a class named Time. The class contains:

• The data fields hour, minute, and second that represent a time.
• A no-arg constructor that creates a Time object for the current time. (The values of the data fields will represent the current time.)
• A constructor that constructs a Time object with a specified elapsed time since midnight, January 1, 1970, in milliseconds. (The values of the data fields will represent this time.)
• A constructor that constructs a Time object with the specified hour, minute, and second.
• Three getter methods for the data fields hour, minute, and second, respectively.
• A method named setTime(long elapseTime) that sets a new time for the object using the elapsed time. For example, if the elapsed time is 555550000 milliseconds, the hour is 10, the minute is 19, and the second is 10.

Draw the UML diagram for the class then implement the class. Write a test program that creates three Time objects (using new Timed, new Time(555550000),and new Time(5, 23, 55)) and displays their hour, minute, and second in the format hour:minute:second.

(Hint: The first two constructors will extract the hour, minute, and second from the elapsed time. For the no-arg constructor, the current time can be obtained using System.currentTimeMillis(), as shown in Listing 2.7, ShowCuncntTime.java. Assume the time is in GMT.)

Program Plan Intro

Program to print the current time with required data fields

Program Plan:

• Define the required public class.
  • Define the main function in the class using public static void main(String[] args).
    • Create the object to the class and pass the arguments.
    • Print the data field using System.out.println() .
  • Close the main function.
• Close the public class definition.
• Define the required class.
  • Define the integers
  • Declare the public function.
    • Define the setter method.
    • Pass the arguments to the public function.
    • Define the getter method.
    • Define the void function.
    • Compute the data fields.
  • Close the main function.
• Close the public class definition.

Program Description Answer

Program Description:

The following java program has the class named Time and shows the current time with the data fields hour, minute and second respectively.

Explanation of Solution

Program:

//Class definition

public class Time {

//Define main function

public static void main(String[] args) {

//Create object to the class and assign the arguments

    MyTime time1 = new MyTime();

    //Print the data field

    System.out.println(time1.getHour() + ":" +

      time1.getMinute() + ":" + time1.getSecond());

    //Create object to the class and assign the arguments

    MyTime time2 = new MyTime(555550000);

    //Print the data field

    System.out.println(time2.getHour() + ":" +

      time2.getMinute() + ":" + time2.getSecond());

    //Create object to the class and assign the arguments

    MyTime time3 = new MyTime(5, 23, 55);

    //Print the data field

    System.out.println(time3.getHour() + ":" +

      time3.getMinute() + ":" + time3.getSecond());

  }

}

//Class definition

class MyTime {

  //Define the integer

  private int hour;

  private int minute;

  private int second;

  //Declare public function

  public MyTime() {

    this(System.currentTimeMillis());

  }

  //Declare public method

  public MyTime(long elapsedTime) {

//Define setter method

    setTime(elapsedTime);

  }

  //Pass the arguments to the public function

  public MyTime(int hour, int minute, int second) {

    this.hour = hour;

    this.minute = minute;

    this.second = second;

  }

  //Define getter method

  public int getHour() {

    return hour;

  }

  //Define getter method

  public int getMinute() {

    return minute;

  }

  //Define getter method

  public int getSecond() {

    return second;

  }

  //Define void function

  public void setTime(long elapsedTime) {

    // Obtain the total seconds since the midnight, Jan 1, 1970

    long totalSeconds = elapsedTime / 1000;

    // Compute the current second in the minute in the hour

    second = (int)(totalSeconds % 60);

    // Obtain the total minutes

    long totalMinutes = totalSeconds / 60;

    // Compute the current minute in the hour

    minute = (int)(totalMinutes % 60);

    // Obtain the total hours

    int totalHours = (int)(totalMinutes / 60);

    // Compute the current hour

    hour = (int)(totalHours % 24);

  }

}

Sample Output

17:57:23

10:19:10

5:23:55