CODEWITHSUNDEEP
java
Mike
Mike

Reputation: 857

How to Subtracting 7hrs from a String time?

I need to convert time from GMT to PST and for that I am trying to subtract 7 hrs from the time. The issue is that the time is stored in a String and I am not sure how can I subtract 7 hrs from a String time. displayDateString gives me the date and time and it is a String. I am trying the following approach but it is not working the way I need it.

Before Code Change

 public static String formatDate(String strDate, String inputFormat, String outputFormat) {
    Date date = convertStringToDate(strDate,inputFormat);
    String displayDateString = formatDate(date, outputFormat);
    DateFormat pstFormat = new SimpleDateFormat();
    return displayDateString;
}

above code outputs: 06/02/17 07:19 PM

After Code Change

public static String formatDate(String strDate, String inputFormat, String outputFormat) {
    Date date = convertStringToDate(strDate,inputFormat);
    String displayDateString = formatDate(date, outputFormat);

    DateFormat pstFormat = new SimpleDateFormat();
    /*TimeZone pstZone = TimeZone.getTimeZone( "PST" );
    pstFormat.setTimeZone( pstZone );
    displayDateString = pstFormat.format(date);*/

    Calendar cal = Calendar.getInstance();
    cal = Calendar.getInstance();
    cal.add( Calendar.HOUR, -7 );
    displayDateString = pstFormat.format( cal.getTime() );
    return displayDateString;
}

public static Date convertStringToDate(String strDate, String inputFormat) {
    SimpleDateFormat dateFormat = null;
    Date date = null;
    boolean formatChagned = false;
    try {
        if(!StringUtils.isSet(strDate)){
            return date;
        }
        if(strDate.indexOf("/")>0 && inputFormat.indexOf("-")>=0){
            inputFormat = inputFormat.replaceAll("-", "/");
            formatChagned=true;
        }else if (strDate.indexOf("-")>0 && inputFormat.indexOf("/")>=0){
            inputFormat = inputFormat.replaceAll("/", "-");
            formatChagned=true;
        }

        dateFormat = new SimpleDateFormat(inputFormat);
        dateFormat.setLenient(false);
        date = dateFormat.parse(strDate);
    } catch (Exception exception) {
        log.error("Given date to parse:"+strDate);
        log.error("Given Input Date Format:"+inputFormat);

        if(formatChagned){
            log.error("Given Input Date Format is incorrcet and it is modified as :"+inputFormat);              
        }

        log.error(exception);
        log.error("DateUtil.convertStringToDate :Parse exception while parsing,"+strDate+" using format :"+inputFormat);
        date = null;
    }
    return date;
}

I added the calendar part to somehow subtract 7hrs from the existing time. This doesn't work.

Upvotes: 1

Views: 107

Answers (2)

Nur Zico
Nur Zico

Reputation: 2447

You may change as following

Calendar cal = Calendar.getInstance();
cal.setTime(new Date(displayDateString));
cal.add(Calendar.HOUR, -7);

Though new Date(displayDateString) is deprecated function

Upvotes: 1

Isac
Isac

Reputation: 1874

You need to set the calendar date before manipulating it:

cal.setTime(date);

before the:

cal.add( Calendar.HOUR, -7 );

And you seem to have some redundant code, like calling the Calendar getInstance twice.

Upvotes: 3

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