Java Timer vs ExecutorService

Question

I have code where I schedule a task using java util Timer  I was looking around and saw ExecutorService can do the same  So this question here  have you used Timer and ExecutorService to schedule tasks  what is the benefit of one using over another   Also wanted to check if anyone had used the Timer class and ran into any issues which the ExecutorService solved for them

User · Accepted Answer

According to Java Concurrency in Practice:

Timer can be sensitive to changes in the system clock, ScheduledThreadPoolExecutor isn't.
Timer has only one execution thread, so long-running task can delay other tasks. ScheduledThreadPoolExecutor can be configured with any number of threads. Furthermore, you have full control over created threads, if you want (by providing ThreadFactory).
Runtime exceptions thrown in TimerTask kill that one thread, thus making Timer dead :-( ... i.e. scheduled tasks will not run anymore. ScheduledThreadExecutor not only catches runtime exceptions, but it lets you handle them if you want (by overriding afterExecute method from ThreadPoolExecutor). Task which threw exception will be canceled, but other tasks will continue to run.

If you can use ScheduledThreadExecutor instead of Timer, do so.

One more thing... while ScheduledThreadExecutor isn't available in Java 1.4 library, there is a Backport of JSR 166 (java.util.concurrent) to Java 1.2, 1.3, 1.4, which has the ScheduledThreadExecutor class.

User · Answer

ExecutorService is newer and more general   A timer is just a thread that periodically runs stuff you have scheduled for it   An ExecutorService may be a thread pool  or even spread out across other systems in a cluster and do things like one-off batch execution  etc     Just look at what each offers to decide

User · Answer

Here s some more good practices around Timer use   http   tech puredanger com 2008 09 22 timer-rules   In general  I d use Timer for quick and dirty stuff and Executor for more robust usage

User · Answer

If it s available to you  then it s difficult to think of a reason not to use the Java 5 executor framework  Calling   ScheduledExecutorService ex   Executors newSingleThreadScheduledExecutor      will give you a ScheduledExecutorService with similar functionality to Timer  i e  it will be single-threaded  but whose access may be slightly more scalable  under the hood  it uses concurrent structures rather than complete synchronization as with the Timer class   Using a ScheduledExecutorService also gives you advantages such as    You can customize it if need be  see the newScheduledThreadPoolExecutor   or the ScheduledThreadPoolExecutor class  The  one off  executions can return results   About the only reasons for sticking to Timer I can think of are    It is available pre Java 5 A similar class is provided in J2ME  which could make porting your application easier  but it wouldn t be terribly difficult to add a common layer of abstraction in this case

User · Answer

From Oracle documentation page on ScheduledThreadPoolExecutor     A ThreadPoolExecutor that can additionally schedule commands to run after a given delay  or to execute periodically  This class is preferable to Timer when multiple worker threads are needed  or when the additional flexibility or capabilities of ThreadPoolExecutor  which this class extends  are required    ExecutorService ThreadPoolExecutor or ScheduledThreadPoolExecutor is obvious choice when you have multiple worker threads    Pros of ExecutorService over Timer   Timer can t take advantage of available CPU cores unlike  ExecutorService especially with multiple tasks using flavours of ExecutorService like ForkJoinPool ExecutorService provides collaborative API if you need coordination between multiple tasks  Assume that you have to submit N number of worker tasks and wait for completion of all of them  You can easily achieve it with invokeAll API  If you want to achieve the same with multiple Timer tasks  it would be not simple   ThreadPoolExecutor provides better API for management of Thread life cycle      Thread pools address two different problems  they usually provide improved performance when executing large numbers of asynchronous tasks  due to reduced per-task invocation overhead  and they provide a means of bounding and managing the resources  including threads  consumed when executing a collection of tasks  Each ThreadPoolExecutor also maintains some basic statistics  such as the number of completed tasks   Few advantages   a  You can create manage control life cycle of Threads  amp  optimize thread creation cost overheads  b  You can control processing of tasks   Work Stealing  ForkJoinPool  invokeAll  etc   c  You can monitor the progress and health of threads  d  Provides better exception handling mechanism

User · Answer

If it s available to you  then it s difficult to think of a reason not to use the Java 5 executor framework  Calling   ScheduledExecutorService ex   Executors newSingleThreadScheduledExecutor      will give you a ScheduledExecutorService with similar functionality to Timer  i e  it will be single-threaded  but whose access may be slightly more scalable  under the hood  it uses concurrent structures rather than complete synchronization as with the Timer class   Using a ScheduledExecutorService also gives you advantages such as    You can customize it if need be  see the newScheduledThreadPoolExecutor   or the ScheduledThreadPoolExecutor class  The  one off  executions can return results   About the only reasons for sticking to Timer I can think of are    It is available pre Java 5 A similar class is provided in J2ME  which could make porting your application easier  but it wouldn t be terribly difficult to add a common layer of abstraction in this case

User · Answer

My reason for sometimes preferring Timer over Executors newSingleThreadScheduledExecutor   is that I get much cleaner code when I need the timer to execute on daemon threads   compare   private final ThreadFactory threadFactory   new ThreadFactory         public Thread newThread Runnable r            Thread t   new Thread r           t setDaemon true           return t           private final ScheduledExecutorService timer   Executors newSingleThreadScheduledExecutor threadFactory      with   private final Timer timer   new Timer true     I do this when I don t need the robustness of an executorservice

User · Answer

ExecutorService is newer and more general   A timer is just a thread that periodically runs stuff you have scheduled for it   An ExecutorService may be a thread pool  or even spread out across other systems in a cluster and do things like one-off batch execution  etc     Just look at what each offers to decide

User · Answer

Here s some more good practices around Timer use   http   tech puredanger com 2008 09 22 timer-rules   In general  I d use Timer for quick and dirty stuff and Executor for more robust usage

User · Answer

If it s available to you  then it s difficult to think of a reason not to use the Java 5 executor framework  Calling   ScheduledExecutorService ex   Executors newSingleThreadScheduledExecutor      will give you a ScheduledExecutorService with similar functionality to Timer  i e  it will be single-threaded  but whose access may be slightly more scalable  under the hood  it uses concurrent structures rather than complete synchronization as with the Timer class   Using a ScheduledExecutorService also gives you advantages such as    You can customize it if need be  see the newScheduledThreadPoolExecutor   or the ScheduledThreadPoolExecutor class  The  one off  executions can return results   About the only reasons for sticking to Timer I can think of are    It is available pre Java 5 A similar class is provided in J2ME  which could make porting your application easier  but it wouldn t be terribly difficult to add a common layer of abstraction in this case

User · Answer

From Oracle documentation page on ScheduledThreadPoolExecutor     A ThreadPoolExecutor that can additionally schedule commands to run after a given delay  or to execute periodically  This class is preferable to Timer when multiple worker threads are needed  or when the additional flexibility or capabilities of ThreadPoolExecutor  which this class extends  are required    ExecutorService ThreadPoolExecutor or ScheduledThreadPoolExecutor is obvious choice when you have multiple worker threads    Pros of ExecutorService over Timer   Timer can t take advantage of available CPU cores unlike  ExecutorService especially with multiple tasks using flavours of ExecutorService like ForkJoinPool ExecutorService provides collaborative API if you need coordination between multiple tasks  Assume that you have to submit N number of worker tasks and wait for completion of all of them  You can easily achieve it with invokeAll API  If you want to achieve the same with multiple Timer tasks  it would be not simple   ThreadPoolExecutor provides better API for management of Thread life cycle      Thread pools address two different problems  they usually provide improved performance when executing large numbers of asynchronous tasks  due to reduced per-task invocation overhead  and they provide a means of bounding and managing the resources  including threads  consumed when executing a collection of tasks  Each ThreadPoolExecutor also maintains some basic statistics  such as the number of completed tasks   Few advantages   a  You can create manage control life cycle of Threads  amp  optimize thread creation cost overheads  b  You can control processing of tasks   Work Stealing  ForkJoinPool  invokeAll  etc   c  You can monitor the progress and health of threads  d  Provides better exception handling mechanism

User · Answer

ExecutorService is newer and more general   A timer is just a thread that periodically runs stuff you have scheduled for it   An ExecutorService may be a thread pool  or even spread out across other systems in a cluster and do things like one-off batch execution  etc     Just look at what each offers to decide

User · Answer

Here s some more good practices around Timer use   http   tech puredanger com 2008 09 22 timer-rules   In general  I d use Timer for quick and dirty stuff and Executor for more robust usage

User · Answer

If it s available to you  then it s difficult to think of a reason not to use the Java 5 executor framework  Calling   ScheduledExecutorService ex   Executors newSingleThreadScheduledExecutor      will give you a ScheduledExecutorService with similar functionality to Timer  i e  it will be single-threaded  but whose access may be slightly more scalable  under the hood  it uses concurrent structures rather than complete synchronization as with the Timer class   Using a ScheduledExecutorService also gives you advantages such as    You can customize it if need be  see the newScheduledThreadPoolExecutor   or the ScheduledThreadPoolExecutor class  The  one off  executions can return results   About the only reasons for sticking to Timer I can think of are    It is available pre Java 5 A similar class is provided in J2ME  which could make porting your application easier  but it wouldn t be terribly difficult to add a common layer of abstraction in this case

User · Answer

My reason for sometimes preferring Timer over Executors newSingleThreadScheduledExecutor   is that I get much cleaner code when I need the timer to execute on daemon threads   compare   private final ThreadFactory threadFactory   new ThreadFactory         public Thread newThread Runnable r            Thread t   new Thread r           t setDaemon true           return t           private final ScheduledExecutorService timer   Executors newSingleThreadScheduledExecutor threadFactory      with   private final Timer timer   new Timer true     I do this when I don t need the robustness of an executorservice

User · Answer

Here s some more good practices around Timer use   http   tech puredanger com 2008 09 22 timer-rules   In general  I d use Timer for quick and dirty stuff and Executor for more robust usage

User · Answer

ExecutorService is newer and more general   A timer is just a thread that periodically runs stuff you have scheduled for it   An ExecutorService may be a thread pool  or even spread out across other systems in a cluster and do things like one-off batch execution  etc     Just look at what each offers to decide

[java] Java Timer vs ExecutorService?

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