每X秒运行一次代码（Java）

Question

This is not super necessary, I am just curious to see what others think. I know it is useless, it's just for fun.

Now I know how to do this, it's fairly simple. I am just trying to figure out a way to do this differently that doesn't require new variables to be created crowding up my class.

Here's how I would do it:

float timePassed = 0f;
public void update(){
    timePassed += deltatime;//Deltatime is just a variable that represents the time passed from one update to another in seconds (it is a float)
    if(timePassed >= 5){
        //code to be ran every 5 seconds
        timePassed -= 5f;
    }
}

What I want to know is if there is a way to do this without the time passed variable. I have a statetime (time since loop started) variable that I use for other things that could be used for this.

Answer 1

If the goal really is to run code every X seconds, my first choice would be to use a util.Timer. Another option is to use a ScheduledExecutorService which adds a couple enhancements over the util.Timer (better Exception handling, for one).

I tend to avoid the Swing.Timer, as I prefer to leave the EDT (event dispatch thread) uncluttered.

Many people write a "game loop" which is closer to what you have started. A search on "game loop" will probably get you several variants, depending on whether you wish to keep a steady rate or not.

Sometimes, in situations where one doesn't want to continually test and reset, one can combine the two functions via the use of an "AND" operation. For example, if you AND 63 to an integer, you have the range 0-63 to iterate through. This works well on ranges that are a power of 2.

Depending on the structure of your calling code, you might pass in the "statetime" variable as a parameter and test if it is larger than your desired X. If you did this, I assume that a step in the called code will reset "statetime" to zero.

Another idea is to pass in a "startTime" to the update method. Then, your timer will test the difference between currentTimeMillis and startTime to see if X seconds has elapsed or not. Again, the code you call should probably set a new "startTime" as part of the process. The nice thing about this method is that there is no need to increment elapsed time.

As long as I am churning out ideas: could also create a future "targetTime" variable and test if currentTimeMillis() - targetTime > 0.

startTime or targetTime can be immutable, which often provides a slight plus, depending on how they are used.