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Thread: time a program

  1. #1
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    Default time a program

    Hi.
    How can I time my while loop to executeevery 3 seconds?

    Here is my code:
    class Info{			
    			public String name;
    			public String version;
    			public String arch;
    			double CPUSpeed;
    		};
    		Info info =  new Info();
    		Info[] queue = new Info[100];
     
    		int pos = 0;
     
    		for(int i=0;i<100;++i)
    		  queue[i]  = new Info();
     
    		Date d = new Date();
    		long start = d.getTime();
     
    		System.out.println("The starting time is "+ start);
    		while(true){
    			long time = d.getTime();
    			if( (start-time)%3 == 0 )
     
    				System.out.println("The current time is "+ time);
    /*				queue[pos].name = System.getProperty("os.name");
    				System.out.println( queue[pos].name);
    				queue[pos].version = System.getProperty("os.version");
    				queue[pos].arch = System.getProperty("os.arch");
    				pos++;
    */
    		}
    I seem to have done it right, but it doesn't work...
    What is wrong?

    Thanks in advance


  2. #2
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    Default Re: time a program

    Use a Timer rather than a while( true ) loop.

  3. #3
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    Default Re: time a program

    Quote Originally Posted by GregBrannon View Post
    Use a Timer rather than a while( true ) loop.
    How?Timer is a cless or what?

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    Default Re: time a program

    Your code does not work at all.
    If you create a Date object it will not start counting up. It will always return the same time when you call the getTime() method.

    There is 2 ways you can do it, either you try to implement this yourself (which is always nice if you want to learn something) or you use the standard classes which give you this functionality.
    One of the standard classes you can use is the Timer class from Swing. Read the API for this class if you want more information:
    Timer (Java Platform SE 7 )
    or
    How to Use Swing Timers (The Javaô Tutorials > Creating a GUI With JFC/Swing > Using Other Swing Features)


    If you want to do it yourself you should use System.nanoTime(); to get the current time in nanoseconds.
    In between checks you should call Thread.yield(); to make the current thread sleep for a short period of time, or Thread.sleep(int millis); to make the thread sleep for a specified amount of time.

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    Default Re: time a program

    Quote Originally Posted by Cornix View Post
    Your code does not work at all.
    If you create a Date object it will not start counting up. It will always return the same time when you call the getTime() method.

    There is 2 ways you can do it, either you try to implement this yourself (which is always nice if you want to learn something) or you use the standard classes which give you this functionality.
    One of the standard classes you can use is the Timer class from Swing. Read the API for this class if you want more information:
    Timer (Java Platform SE 7 )
    or
    How to Use Swing Timers (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Other Swing Features)


    If you want to do it yourself you should use System.nanoTime(); to get the current time in nanoseconds.
    In between checks you should call Thread.yield(); to make the current thread sleep for a short period of time, or Thread.sleep(int millis); to make the thread sleep for a specified amount of time.
    In between what checks?

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    Default Re: time a program

    If you check for how much time has passed.
    Since a simple if is incredibly fast you would check thousands of times per second, thats very inefficient use of CPU cycles.
    After you checked how much time has passed call yield or sleep to prevent busy waiting.

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    Default Re: time a program

    I used TimeUnit.
    But now I want to specify a period, say executing function A() for 5 minutes and then execute function B()

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    Default Re: time a program

    Have method A keep track of how long it can execute and when the time is up, method A should exit so that method B can execute.
    If you don't understand my answer, don't ignore it, ask a question.

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