Java: Getting time interval

Question

I am on a project to capture the interval time in hh:mm. I have 2 buttons named btnTimeOut & btnTimeIn both capturing the system time when clicked. The requirement is to get the interval between the btnTimeOut & btnTime in hh:mm, etc. 12:30 - 10:00 = 02:30 (hh:mm).

Currently I used the following codes for the interval but it returns as minutes, etc. 12:30 - 10:00 = 150 minutes.

  String timeOut = lblTimeOut.getText();
  String timeIn = lblTimeIn2.getText();

  SimpleDateFormat format = new SimpleDateFormat("hh:mm");

  Date d1 = null;
  Date d2 = null;

  try {
      d1 = format.parse(timeOut);
      d2 = format.parse(timeIn);
  } 
  catch (Exception e){
      e.printStackTrace();
  }

  long diff = d2.getTime() - d1.getTime();
  long diffMinutes = diff / (60 * 1000);         
  long diffHours = diff / (60 * 60 * 1000);  

  lblSurface.setText(String.valueOf(diffMinutes)); 

How to get the duration in the form hh:mm?

I used Joda time and return with Invalid format: "12:19" is malformed at ":19". As for my other buttons which trigger the display time.

DateFormat timeFormat = new SimpleDateFormat("hh:mm");
Date date = new Date();  
String time = timeFormat.format(date);  
lblTimeIn2.setText(time);

Timer timer = new Timer(1000, timerListener);  
    // to make sure it doesn't wait one second at the start  
timer.setInitialDelay(0);  
timer.start();   
}         

I've no idea what is wrong, do I need to use joda time for displaying time for my other label too?

Answer 1

When you are getting minutes, it includes the hours as well. Simply divide the minutes by 60 to get the hours and update the minutes with remainder value of the division as below.

    long diffMinutes = diff / (60 * 1000);  //difference in minutes       
    long diffHours = (long) diffMinutes/60; //get hours from diff minutes
    diffMinutes  = diffMinutes % 60; //remainder of minutes after converting hours

Finally set the hours and minutes in the text:

     lblSurface.setText(diffHours + ":" + diffMinutes);

Since ":" is appended in between, it should be fine because of implicit conversion.

Answer 2

String.format("%1d:%2d", mins/60, (mins%60))

E.G.

public class HoursMinutesFormat {

    public static void main(String[] args) {
        int mins = 150;
        System.out.println(String.format("%1d:%2d", mins/60, (mins%60)));
    }
}

Output

2:30

Answer 3

I, personally, would use JodaTime as it takes into account things like difference between days (ie the difference between 23:30-02:30) and has nice inbuilt formatters

public class TestJodaTime {

    public static void main(String[] args) {

        DateTime start = new DateTime(2012, 11, 11, 23, 30, 0, 0);
        DateTime end = new DateTime(2012, 11, 12, 1, 30, 0, 0);
        Interval interval = new Interval(start, end);
        Period toPeriod = interval.toPeriod();

        PeriodFormatter dateFormat = new PeriodFormatterBuilder()
                        .printZeroAlways().minimumPrintedDigits(2)
            .appendHours().minimumPrintedDigits(2)
            .appendSeparator(":")
            .appendMinutes().minimumPrintedDigits(2)
            .toFormatter();        
        System.out.println(toPeriod.toString(dateFormat));
    }
}

Which will output 02:00

Extended example

public class TestJodaTime {

    public static void main(String[] args) {
        new TestJodaTime();
    }

    public TestJodaTime() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JodaPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class JodaPane extends JPanel {

        private JTextField startHour;
        private JTextField startMin;
        private JTextField endHour;
        private JTextField endMin;
        private JButton diffButton;
        private JLabel lblDiff;
        private JButton markStart;
        private JButton markEnd;
        private Timer timer;
        private JLabel realTime;

        public JodaPane() {

            markStart = new JButton("Mark");
            markEnd = new JButton("Mark");

            startHour = new JTextField(2);
            startMin = new JTextField(2);
            endHour = new JTextField(2);
            endMin = new JTextField(2);
            diffButton = new JButton("=");
            lblDiff = new JLabel("00:00");
            realTime = new JLabel("00:00.00");

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.WEST;
            add(new JLabel("From"), gbc);
            gbc.gridx++;
            add(startHour, gbc);
            gbc.gridx++;
            add(new JLabel(":"), gbc);
            gbc.gridx++;
            add(startMin, gbc);
            gbc.gridx++;
            add(markStart, gbc);
            gbc.gridx++;
            add(new JLabel(" to "), gbc);
            gbc.gridx++;
            add(endHour, gbc);
            gbc.gridx++;
            add(new JLabel(":"), gbc);
            gbc.gridx++;
            add(endMin, gbc);
            gbc.gridx++;
            add(markEnd, gbc);
            gbc.gridx++;
            add(diffButton, gbc);
            gbc.gridx++;
            add(lblDiff, gbc);

            gbc.gridy++;
            add(realTime, gbc);

            diffButton.addActionListener(new ActionListener() {
                public boolean isValid(JTextField field) {
                    return field.getText() != null && field.getText().length() > 0;
                }
                @Override
                public void actionPerformed(ActionEvent ae) {
                    if (isValid(startHour) && isValid(startMin)
                                    && isValid(endHour) && isValid(endMin)) {
                        int hourStart = Integer.parseInt(startHour.getText());
                        int minStart = Integer.parseInt(startMin.getText());
                        int hourEnd = Integer.parseInt(endHour.getText());
                        int minEnd = Integer.parseInt(endMin.getText());

                        String prefix = "";
                        if (hourEnd < hourStart) {
                            int tmp = hourStart;
                            hourStart = hourEnd;
                            hourEnd = tmp;
                            prefix = "-";
                        }

                        System.out.println("Start = " + hourStart + ":" + minStart);
                        System.out.println("End = " + hourEnd + ":" + minEnd);

                        DateTime start = new DateTime(0, 1, 1, hourStart, minStart, 0, 0);
                        DateTime end = new DateTime(0, 1, 1, hourEnd, minEnd, 0, 0);
                        Interval interval = new Interval(start, end);
                        Period toPeriod = interval.toPeriod();

                        PeriodFormatter dateFormat = new PeriodFormatterBuilder()
                                        .printZeroAlways().minimumPrintedDigits(2)
                                        .appendHours().minimumPrintedDigits(2)
                                        .appendSeparator(":")
                                        .appendMinutes().minimumPrintedDigits(2)
                                        .toFormatter();
                        lblDiff.setText(prefix + dateFormat.print(toPeriod));
                    }
                }

            });

            markStart.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent ae) {
                    Calendar cal = Calendar.getInstance();
                    startHour.setText(Integer.toString(cal.get(Calendar.HOUR_OF_DAY)));
                    startMin.setText(Integer.toString(cal.get(Calendar.MINUTE)));
                    diffButton.doClick();
                }

            });
            markEnd.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent ae) {
                    Calendar cal = Calendar.getInstance();
                    endHour.setText(Integer.toString(cal.get(Calendar.HOUR_OF_DAY)));
                    endMin.setText(Integer.toString(cal.get(Calendar.MINUTE)));
                    diffButton.doClick();
                }

            });

            timer = new Timer(500, new ActionListener() {
                private SimpleDateFormat sdf = new SimpleDateFormat("HH:mm.ss");
                @Override
                public void actionPerformed(ActionEvent ae) {
                    realTime.setText(sdf.format(new Date()));
                }
            });
            timer.setRepeats(true);
            timer.setCoalesce(true);
            timer.start();


        }

    }

}

Your questions a little vague, so I've done a wide example. Mark, basically auto fills the fields with the current time.

There is little validation ;)