Addition and Subtraction of Dates in Java

Question

How can we add or subtract date in java? For instance java.sql.Date and formatted like this: yyyy-MM-dd, how can i Add 5 months from that? I've seen in some tutorial that they are using Calendar, can we set date on it? Please Help.

Example: 2012-01-01 when added 5 months will become 2012-06-01.

PS: I'm a .Net Programmer and slowly learning to Java environment.

Answer 1

First of all you have to convert your String date to java.util.Date, than you have to use java.util.Calendar to manipulate dates. It is also possible to do math with millis, but I do not recommend this.

public static void main( final String[] args ) throws ParseException {
    final String sdate = "2012-01-01";
    final SimpleDateFormat df = new SimpleDateFormat( "yyyy-MM-dd" );
    final Date date = df.parse( sdate ); // conversion from String
    final java.util.Calendar cal = GregorianCalendar.getInstance();
    cal.setTime( date );
    cal.add( GregorianCalendar.MONTH, 5 ); // date manipulation
    System.out.println( "result: " + df.format( cal.getTime() ) ); // conversion to String
}

Answer 2

Stear clear of the built-in Date class for date math. Take a look at JodaTime, which has a much better API for this kind of thing.