Convert time field H:M into integer field (minutes) in JAVA

Question

The JTable includes the time field, e.g. "01:50". I need to read this value into the integer variable. For this I´d like to convert time into minutes. For instance "01:50" should be converted into 110.

To solve the task, first I saved the time value as a String.

String minutS = tableModel.getValueAt(1,1).toString();

Secondly, I´m going to process this String and extract the integers before and after the symbol :. Finally I will calculate the total minutes. Is this solution efficient? Perhaps, it´s possible to substitute it with Calendar or sth like this?

Answer 1

I don't think using Calendar/Date will be better than straightforward parse for this case. If your time format is indeed H:m, then I don't think you need anything more complex than this:

/**
 * @param s H:m timestamp, i.e. [Hour in day (0-23)]:[Minute in hour (0-59)]
 * @return total minutes after 00:00
 */
private static int toMins(String s) {
    String[] hourMin = s.split(":");
    int hour = Integer.parseInt(hourMin[0]);
    int mins = Integer.parseInt(hourMin[1]);
    int hoursInMins = hour * 60;
    return hoursInMins + mins;
}

Answer 2

Look the sample below which we are using in our application

public static int toMinutes( String sDur, boolean bAssumeMinutes ) throws NumberFormatException {
        /* Use of regular expressions might be better */
        int iMin = 0;
        int iHr = 0;
        sDur = sDur.trim();
        //find punctuation
        int i = sDur.indexOf(":");//HH:MM
        if (i < 0) {
            //no punctuation, so assume whole thing is an number
            //double dVal = Double.parseDouble(sDur);
            double dVal = ParseAndBuild.parseDouble(sDur, Double.NaN);
            if (Double.isNaN(dVal)) throw new NumberFormatException(sDur);
            if (!bAssumeMinutes) {
                //decimal hours so add half a minute then truncate to minutes
                iMin = (int)((dVal * 60.0) + (dVal < 0 ? -0.5 : 0.5));
            } else {
                iMin = (int)dVal;
            }
        }
        else {
            StringBuffer sBuf = new StringBuffer(sDur);
            int j = sBuf.indexOf(MINUS_SIGN);
            //check for negative sign
            if (j >= 0) {
                //sign must be leading/trailing but either allowed regardless of MINUS_SIGN_TRAILS
                if (j > 0 && j < sBuf.length() -1)
                    throw new NumberFormatException(sDur);                  
                sBuf.deleteCharAt(j);
                i = sBuf.indexOf(String.valueOf(":"));
            }
            if (i > 0)
                iHr = Integer.parseInt(sBuf.substring(0, i)); //no thousands separators allowed
            if (i < sBuf.length() - 1)
                iMin = Integer.parseInt(sBuf.substring(i+1));
            if (iMin < 0 || (iHr != 0 && iMin >= 60))
                throw new NumberFormatException(sDur);
            iMin += iHr * 60;
            if (j >= 0) iMin = -iMin;
        }
        return iMin;
    }