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Java Forum / First Aid / May 2004Time arithmetic
Dear all, How can I subtract two dates formatted like '01/04/03 12:02' and '01/04/03 11:38' and find their difference in minutes. Cheers! >How can I subtract two dates formatted like '01/04/03 12:02' and '01/04/03 >11:38' and find their difference in minutes. see http://mindprod.com/jgloss/calendar.html just subtract the timestamps in milliseconds and divide by 60*1000. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. > >How can I subtract two dates formatted like '01/04/03 12:02' and '01/04/03 > >11:38' and find their difference in minutes. > see http://mindprod.com/jgloss/calendar.html > > just subtract the timestamps in milliseconds and divide by 60*1000. is there some "default" time stamp with which all objects are stamped when they're instantiated? javac@mail.com http://www.geocities.com/cjavacjava/ >is there some "default" time stamp with which all objects are stamped >when they're instantiated? Date objects contain the time they were created. Ordinary objects to not. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. > >is there some "default" time stamp with which all objects are stamped > >when they're instantiated? > > Date objects contain the time they were created. Ordinary objects to > not. how would i start a "start watch" to count the time (milliseconds?) from instantiation, please? for ordinary objects, of course. thanks, javac@mail.com http://www.geocities.com/cjavacjava/ >how would i start a "start watch" to count the time (milliseconds?) >from instantiation, please? for ordinary objects, of course. see http://mindprod.com/jgloss/time.html -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. > >how would i start a "start watch" to count the time (milliseconds?) > >from instantiation, please? for ordinary objects, of course. > see http://mindprod.com/jgloss/time.html thanks Roedy, i'm hesitant to use a date generated _by_ the system clock, since system clocks aren't necesarilly (sp) accurate. is there an alternative sort of ready-made object with a "time" of zero that simply counts up, or should I make my own? thanks, javac@mail.com http://www.geocities.com/cjavacjava/ >i'm hesitant to use a date generated _by_ the system clock, since >system clocks aren't necesarilly (sp) accurate. is there an >alternative sort of ready-made object with a "time" of zero that >simply counts up, or should I make my own? See http://mindprod.com/jgloss/setclock.html and http://mindprod.com/jgloss/ntp.html if you want very precise time. If all you want is relative time, the system clock is fine, even if it is inaccurate. If all you want is a sequence number for objects, use static seq++ which will be faster by far than the clock. CPUS have additional clocks besides the ticker. To get at them you would have to write JNI. Perhaps if I knew what you were trying to accomplish I could direct you better. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. [..] > If all you want is relative time, the system clock is fine, even if it > is inaccurate. > > If all you want is a sequence number for objects, use static seq++ > which will be faster by far than the clock. [..] > Perhaps if I knew what you were trying to accomplish I could direct > you better. relative time is all i want. life forms are born and die, each life form'll have a life span (in miliseconds, presumably). when their age >= life span, or for other reason, then that life form'll die. i don't like the idea of a system clock because i might be serializing the life forms for storage, and that'd involve more arithmetic than a simple timer that only counts "up" while the life form exists -- like a stopwatch. thanks, javac@mail.com http://www.geocities.com/cjavacjava/ >relative time is all i want. For you own objects you can just use a sequence number you increment any time you allocate something. To make it easier, you might have private static int sequence = 0; per class. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. > >how would i start a "start watch" to count the time (milliseconds?) > >from instantiation, please? for ordinary objects, of course. > see http://mindprod.com/jgloss/time.html thanks Roedy, i'm hesitant to use a date generated _by_ the system clock, since system clocks aren't necesarilly (sp) accurate. is there an alternative sort of ready-made object with a "time" of zero that simply counts up, or should I make my own? thanks, javac@mail.com http://www.geocities.com/cjavacjava/ Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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