public static Date getPreviousDay(Date dt) {
        if (dt == null) {
            return dt;
        }

        Calendar cal = Calendar.getInstance();
        cal.setTime(dt);
        cal.add(Calendar.DAY_OF_YEAR, -1);
        return cal.getTime();
    }
public static Date getPreviousDay ( Date dt ) { if ( dt == null ) { return dt ; } Calendar cal = Calendar . getInstance ( ) ; cal . setTime ( dt ) ; cal . add ( Calendar . DAY_OF_YEAR , - 1 ) ; return cal . getTime ( ) ; }
added by zhuqian 2009-03-25