Is FileChannel.position() thread safe?












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Is it safe to write from different threads to one file using FileChannel.position()? This is necessary for multipart downloading. Each thread will write to its position in the file, i.e. the positions of the thread will not intersect.










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    0















    Is it safe to write from different threads to one file using FileChannel.position()? This is necessary for multipart downloading. Each thread will write to its position in the file, i.e. the positions of the thread will not intersect.










    share|improve this question

























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      Is it safe to write from different threads to one file using FileChannel.position()? This is necessary for multipart downloading. Each thread will write to its position in the file, i.e. the positions of the thread will not intersect.










      share|improve this question














      Is it safe to write from different threads to one file using FileChannel.position()? This is necessary for multipart downloading. Each thread will write to its position in the file, i.e. the positions of the thread will not intersect.







      java android filechannel






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      asked Nov 18 '18 at 10:12









      proninyaroslavproninyaroslav

      60210




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          While the individual option is thread safe, it's not thread local and changing it will be visible to all threads.



          The simplest option is to create a FileChannel for each thread which avoid any interactions unless you write to the file in which case those changes can be seen.






          share|improve this answer
























          • Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

            – proninyaroslav
            Nov 18 '18 at 13:19













          • @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

            – Peter Lawrey
            Nov 18 '18 at 16:22



















          0














          In the FileChannel Documentation, it says:




          File channels are safe for use by multiple concurrent threads.







          share|improve this answer
























          • While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

            – Peter Lawrey
            Nov 18 '18 at 12:42











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          2 Answers
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          active

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          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          2














          While the individual option is thread safe, it's not thread local and changing it will be visible to all threads.



          The simplest option is to create a FileChannel for each thread which avoid any interactions unless you write to the file in which case those changes can be seen.






          share|improve this answer
























          • Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

            – proninyaroslav
            Nov 18 '18 at 13:19













          • @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

            – Peter Lawrey
            Nov 18 '18 at 16:22
















          2














          While the individual option is thread safe, it's not thread local and changing it will be visible to all threads.



          The simplest option is to create a FileChannel for each thread which avoid any interactions unless you write to the file in which case those changes can be seen.






          share|improve this answer
























          • Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

            – proninyaroslav
            Nov 18 '18 at 13:19













          • @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

            – Peter Lawrey
            Nov 18 '18 at 16:22














          2












          2








          2







          While the individual option is thread safe, it's not thread local and changing it will be visible to all threads.



          The simplest option is to create a FileChannel for each thread which avoid any interactions unless you write to the file in which case those changes can be seen.






          share|improve this answer













          While the individual option is thread safe, it's not thread local and changing it will be visible to all threads.



          The simplest option is to create a FileChannel for each thread which avoid any interactions unless you write to the file in which case those changes can be seen.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 18 '18 at 12:44









          Peter LawreyPeter Lawrey

          444k56566967




          444k56566967













          • Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

            – proninyaroslav
            Nov 18 '18 at 13:19













          • @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

            – Peter Lawrey
            Nov 18 '18 at 16:22



















          • Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

            – proninyaroslav
            Nov 18 '18 at 13:19













          • @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

            – Peter Lawrey
            Nov 18 '18 at 16:22

















          Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

          – proninyaroslav
          Nov 18 '18 at 13:19







          Do I understand correctly that creating two different channels will allow me to safely move seek pointer for writing in the file? In other words, if the second thread moves seek pointer to the other position of the file, it will not be reflected in the first thread and first thread will continue to write data to the old position?

          – proninyaroslav
          Nov 18 '18 at 13:19















          @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

          – Peter Lawrey
          Nov 18 '18 at 16:22





          @proninyaroslav each FileChannel can point to a different position without interfering with each other. If each thread has it's own, they are only sharing the underlying file not the FileChannel.

          – Peter Lawrey
          Nov 18 '18 at 16:22













          0














          In the FileChannel Documentation, it says:




          File channels are safe for use by multiple concurrent threads.







          share|improve this answer
























          • While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

            – Peter Lawrey
            Nov 18 '18 at 12:42
















          0














          In the FileChannel Documentation, it says:




          File channels are safe for use by multiple concurrent threads.







          share|improve this answer
























          • While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

            – Peter Lawrey
            Nov 18 '18 at 12:42














          0












          0








          0







          In the FileChannel Documentation, it says:




          File channels are safe for use by multiple concurrent threads.







          share|improve this answer













          In the FileChannel Documentation, it says:




          File channels are safe for use by multiple concurrent threads.








          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 18 '18 at 10:25









          vollkorntomatevollkorntomate

          3125




          3125













          • While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

            – Peter Lawrey
            Nov 18 '18 at 12:42



















          • While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

            – Peter Lawrey
            Nov 18 '18 at 12:42

















          While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

          – Peter Lawrey
          Nov 18 '18 at 12:42





          While the individual operation is thread safe, it's value is not thread local.and using it with other operations will result in race conditions.

          – Peter Lawrey
          Nov 18 '18 at 12:42


















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