If paint events are expensive, or if you are writing a program that does terminal-style output, you can optimize the scheduling of events by calculating the amount of time remaining until the display will change: long elapsedTime = System.currentTimeMillis() - startTime Just incorporate the timer display call into your regular screen refresh. If you are writing a program with animation of some sort (like a game) which is refreshing the screen 30 times a second, then you need do nothing. This seems a bit of a waste, because 9 times out of 10 you are painting what is already on the screen.
#Java format int as timer counter code#
Because the calculation of the time does not depend on the code being called at a particular point in time, and because it does not matter if you re-paint the screen with the same time, this approach more or less guarantees that the displayed time will show the right time within about 1/10 of a second. One lazy way to do this is to schedule 10 paint events per second. You can request a paint event, but there may be hundreds of other paint events queued up to be handled before yours.
You would like these paint events to come right after the time that the display is expected to change. In a GUI environment you need to schedule paint events. This will depend upon the technology you are using to display with. The second aspect of a timer is refresh of the display. The point is that currentTimeMillis() is the accurate representation of the time regardless of when this code is called - and that is an important consideration because thread and timer events are not guaranteed to be accurate at a specific time. The above calculation will be accurate whether you run this code every second, 100 times a second, or once every 3.572 seconds. This is all completely unnecessary because the OS has a function to tell you the current time. If sleep returns 300ms late one time, that error is compounded into your calculation of what time it is. Code that uses the Thread.sleep(1000) function to loop every second will find that the error builds up over time. If the system is extremely busy (for example page fetching from a faulty disk) it could actually be several seconds late. If the system is busy, that code might be called quite a bit later than the second. The problem is that you can schedule code to be called every second, but there is no guarantee of exactly when that code will be called. something called "elapsedSeconds" which they maintain. The biggest mistake that programmers make is to think they need a variable to hold the current time and then to write code to increment that variable every second, e.g. put here code to format and display the values Long elapsedMinutes = elapsedSeconds / 60 Long secondsDisplay = elapsedSeconds % 60 Long elapsedSeconds = elapsedTime / 1000 long elapsedTime = System.currentTimeMillis() - startTime Later, when you want to display the amount of time, you just subtract this from the current time. Timer code will involve two aspects which many programmers mix up:Īll you need to do to calculate the time to display, is to record the time that the timer started: long startTime = System.currentTimeMillis() The function System.currentTimeMillis() will do that for you, and it does it quite accurately.
You do not need to write code to keep track of the time. That is, they write some sort of loop that increments a variable every second or some such silly thing. If seem that the biggest mistake that programmers make in implementing a timer, is thinking that they need something to keep track of the current time. However, I would caution you that I have seen some very confused answers on stack overflow, in some cases shockingly poor coding habits, so be very careful. It does not store any personal data.This is not difficult. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
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