java run a function after a specific number of seconds

Question

I have a specific function that I want to be executed after 5 seconds  How can i do that in Java   I found javax swing timer  but I can t really understand how to use it  It looks like I m looking for something way simpler then this class provides   Please add a simple usage example

User · Answer

Your original question mentions the  Swing Timer   If in fact your question is related to SWing  then you should be using the Swing Timer and NOT the util Timer   Read the section from the Swing tutorial on  How to Use Timers  for more information

User · Answer

ScheduledThreadPoolExecutor has this ability  but it s quite heavyweight  Timer also has this ability but opens several thread even if used only once  Here s a simple implementation with a test  signature close to Android s Handler postDelayed     public class JavaUtil       public static void postDelayed final Runnable runnable  final long delayMillis            final long requested   System currentTimeMillis            new Thread new Runnable                  Override             public void run                        The while is just to ignore interruption                  while  true                        try                           long leftToSleep   requested   delayMillis - System currentTimeMillis                            if  leftToSleep  gt  0                                Thread sleep leftToSleep                                                     break                        catch  InterruptedException ignored                                                            runnable run                             start             Test   Test public void testRunsOnlyOnce   throws InterruptedException       long delay   100      int num   0      final AtomicInteger numAtomic   new AtomicInteger num       JavaUtil postDelayed new Runnable              Override         public void run                 numAtomic incrementAndGet                     delay       Assert assertEquals num  numAtomic get         Thread sleep delay   10       Assert assertEquals num   1  numAtomic get         Thread sleep delay   2       Assert assertEquals num   1  numAtomic get

User · Answer

you could use the Thread Sleep   function  Thread sleep 4000   myfunction      Your function will execute after 4 seconds  However this might pause the entire program

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My code is as follows   new java util Timer   schedule       new java util TimerTask              Override         public void run                    your code here  and if you have to refresh UI put this code              runOnUiThread new   Runnable                       public void run                                   your code                                                                         5000

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public static Timer t   public synchronized void startPollingTimer             if  t    null                TimerTask task   new TimerTask                      Override                 public void run                          Do your work                                               t   new Timer                t scheduleAtFixedRate task  0  1000

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Example of using javax swing Timer  Timer timer   new Timer 3000  new ActionListener        Override   public void actionPerformed ActionEvent arg0           Code to be executed         timer setRepeats false      Only execute once timer start       Go go go    This code will only be executed once  and the execution happens in 3000 ms  3 seconds    As camickr mentions  you should lookup  How to Use Swing Timers  for a short introduction

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new java util Timer   schedule           new java util TimerTask                  Override             public void run                        your code here                                   5000       EDIT   javadoc says      After the last live reference to a Timer object goes away and all outstanding tasks have completed execution  the timer s task execution thread terminates gracefully  and becomes subject to garbage collection   However  this can take arbitrarily long to occur

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All other unswers require to run your code inside a new thread   In some simple use cases you may just want to wait a bit and continue execution within the same thread flow   Code below demonstrates that technique  Keep in mind this is similar to what java util Timer does under the hood but more lightweight   import java util concurrent TimeUnit  public class DelaySample       public static void main String   args           DelayUtil d   new DelayUtil           System out println  started    new Date            d delay 500          System out println  half second after    new Date            d delay 1  TimeUnit MINUTES           System out println  1 minute after    new Date               DelayUtil Implementation  import java util concurrent TimeUnit  import java util concurrent locks Condition  import java util concurrent locks ReentrantLock   public class DelayUtil                   Delays the current thread execution          The thread loses ownership of any monitors          Quits immediately if the thread is interrupted                param duration the time duration in milliseconds           public void delay final long durationInMillis          delay durationInMillis  TimeUnit MILLISECONDS                        param duration the time duration in the given   code sourceUnit         param unit            public void delay final long duration  final TimeUnit unit            long currentTime   System currentTimeMillis            long deadline   currentTime unit toMillis duration           ReentrantLock lock   new ReentrantLock            Condition waitCondition   lock newCondition             while   deadline-currentTime  gt 0                try                   lock lockInterruptibly                        waitCondition await deadline-currentTime  TimeUnit MILLISECONDS                 catch  InterruptedException e                    Thread currentThread   interrupt                    return                finally                   lock unlock                              currentTime   System currentTimeMillis

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Something like this      When your program starts up ScheduledExecutorService executor   Executors newSingleThreadScheduledExecutor        then  when you want to schedule a task Runnable task            executor schedule task  5  TimeUnit SECONDS       and finally  when your program wants to exit executor shutdown      There are various other factory methods on Executor which you can use instead  if you want more threads in the pool   And remember  it s important to shutdown the executor when you ve finished  The shutdown   method will cleanly shut down the thread pool when the last task has completed  and will block until this happens  shutdownNow   will terminate the thread pool immediately

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As a variation of  tangens answer  if you can t wait for the garbage collector to clean up your thread  cancel the timer at the end of your run method      Timer t   new java util Timer    t schedule           new java util TimerTask                  Override             public void run                        your code here                    close the thread                 t cancel                                      5000

[java] java: run a function after a specific number of seconds

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