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Implications of instantiating multiple Runnable with shared objects?

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1

I have a program that is intended to be multithreaded. I have a ProcessRunnable class that processes data with lots of IO required. The ProcessRunnable classes are all run in separate threads but are instantiated with shared instances of client / util Classes.

Example:

Client client = new Client();
Util util = new Util();

List<Runnable> runnables = new ArrayList<>();

for (int i; i < THREAD_COUNT; i++) 
 runnables.add(ProcessRunnable
 .builder()
 .client(client)
 .util(util)
 .build());


runnables.forEach(runnable -> new Thread(runnable).start());

I'm curious as to whether reusing the same instances of classes in the runnables is blocking behavior and essentially causing my program to become single threaded?

java multithreading runnable

share|improve this question

asked Mar 23 at 4:50

pauldpauld

176213

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  ^sweet^ thanks @AniketSahrawat
  
  – pauld
  Mar 23 at 4:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @GhostCat fair enough - points garnered! Thanks for entering into discussion despite best practices ;)
  
  – pauld
  Mar 23 at 6:19
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  No worries - thanks again!
  
  – pauld
  Mar 23 at 6:30
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You are welcome. And please don't forget about deleting no longer required comments.
  
  – GhostCat
  Mar 23 at 6:42
  

  
  
  
  

add a comment | 

1

I have a program that is intended to be multithreaded. I have a ProcessRunnable class that processes data with lots of IO required. The ProcessRunnable classes are all run in separate threads but are instantiated with shared instances of client / util Classes.

Example:

Client client = new Client();
Util util = new Util();

List<Runnable> runnables = new ArrayList<>();

for (int i; i < THREAD_COUNT; i++) 
 runnables.add(ProcessRunnable
 .builder()
 .client(client)
 .util(util)
 .build());


runnables.forEach(runnable -> new Thread(runnable).start());

I'm curious as to whether reusing the same instances of classes in the runnables is blocking behavior and essentially causing my program to become single threaded?

java multithreading runnable

share|improve this question

asked Mar 23 at 4:50

pauldpauld

176213

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  ^sweet^ thanks @AniketSahrawat
  
  – pauld
  Mar 23 at 4:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @GhostCat fair enough - points garnered! Thanks for entering into discussion despite best practices ;)
  
  – pauld
  Mar 23 at 6:19
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  No worries - thanks again!
  
  – pauld
  Mar 23 at 6:30
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You are welcome. And please don't forget about deleting no longer required comments.
  
  – GhostCat
  Mar 23 at 6:42
  

  
  
  
  

add a comment | 

I have a program that is intended to be multithreaded. I have a ProcessRunnable class that processes data with lots of IO required. The ProcessRunnable classes are all run in separate threads but are instantiated with shared instances of client / util Classes.

Example:

Client client = new Client();
Util util = new Util();

List<Runnable> runnables = new ArrayList<>();

for (int i; i < THREAD_COUNT; i++) 
 runnables.add(ProcessRunnable
 .builder()
 .client(client)
 .util(util)
 .build());


runnables.forEach(runnable -> new Thread(runnable).start());

I'm curious as to whether reusing the same instances of classes in the runnables is blocking behavior and essentially causing my program to become single threaded?

java multithreading runnable

share|improve this question

asked Mar 23 at 4:50

pauldpauld

176213

Client client = new Client();
Util util = new Util();

List<Runnable> runnables = new ArrayList<>();

for (int i; i < THREAD_COUNT; i++) 
 runnables.add(ProcessRunnable
 .builder()
 .client(client)
 .util(util)
 .build());


runnables.forEach(runnable -> new Thread(runnable).start());

share|improve this question

asked Mar 23 at 4:50

pauldpauld

176213

share|improve this question

asked Mar 23 at 4:50

pauldpauld

176213

asked Mar 23 at 4:50

pauldpauld

176213

asked Mar 23 at 4:50

pauldpauld

176213

1 Answer
1

active

oldest

votes

2

Here:

runnable -> new Thread(runnable).start()

The key point that actually makes your code multithreaded is that you call the start() method of your thread objects. If you would just call the run method of the thread class, then you actually end up with the "enclosing" thread doing all the work.

Finally, please note that using "bare" threads directly isn't ideal. It is okay to learn about that, but Java offers important abstractions like the ExecutorService that should be used instead for various reasons.

The main reason to avoid raw threads: you have to control all subtle details manually. How many threads should be used? What about pooling and sharing threads (creating a thread comes with a lot of overhead, so in the real world you avoid creating threads for single tasks to then throw them away, like your code does). Beyond that: typically you want to solve a business problem. You want to use multiple threads to prevent bottle neck situations. Examole: you want to make multiple requests over the network in parallel to fetch and process data. Then you really only care about the end result, and not about low level threading subtleties! Then you would for example use Future or CompleteableFuture objects.

Simply use a search engine and research those terms, you will find plenty of material.

share|improve this answer

edited Mar 23 at 5:24

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  thanks for your comment! Would you mind elaborating on the advantages provided by using the ExecutorService and or recommend any reading material that you think is particularly illuminating? The threads are sharing state via BlockingQueues/BlockingDeques - I found it relatively simple to manage / end the threads appropriately based of the the BlocksQueues but of course would love to understand a better way of doing things!
  
  – pauld
  Mar 23 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The code shown above is simplified to the scope of the original question. The threads used are not thrown away but are long running and draw from a PriorityBlockingQueue one item at a time to process. I definitely see how this could be improved using ExecutorService to manage threads. Currently all the processing steps are encapsulated in ProcessRunnable including multiple IO calls - do you think there would be performance differences from splitting up each step and using CompletableFuture on all IO vs submitting a list of Runnables for the executor service to process/execute?
  
  – pauld
  Mar 23 at 6:02
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also - I know how to use a search engine! Not to be flippant or lazy, just asking if you yourself have found any sources you think explain or show things in a particularly helpful way. You seem to have the creds to where its worth asking the question!
  
  – pauld
  Mar 23 at 6:07
  

  
  
  
  

add a comment | 

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2

Here:

runnable -> new Thread(runnable).start()

The key point that actually makes your code multithreaded is that you call the start() method of your thread objects. If you would just call the run method of the thread class, then you actually end up with the "enclosing" thread doing all the work.

Finally, please note that using "bare" threads directly isn't ideal. It is okay to learn about that, but Java offers important abstractions like the ExecutorService that should be used instead for various reasons.

The main reason to avoid raw threads: you have to control all subtle details manually. How many threads should be used? What about pooling and sharing threads (creating a thread comes with a lot of overhead, so in the real world you avoid creating threads for single tasks to then throw them away, like your code does). Beyond that: typically you want to solve a business problem. You want to use multiple threads to prevent bottle neck situations. Examole: you want to make multiple requests over the network in parallel to fetch and process data. Then you really only care about the end result, and not about low level threading subtleties! Then you would for example use Future or CompleteableFuture objects.

Simply use a search engine and research those terms, you will find plenty of material.

share|improve this answer

edited Mar 23 at 5:24

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  thanks for your comment! Would you mind elaborating on the advantages provided by using the ExecutorService and or recommend any reading material that you think is particularly illuminating? The threads are sharing state via BlockingQueues/BlockingDeques - I found it relatively simple to manage / end the threads appropriately based of the the BlocksQueues but of course would love to understand a better way of doing things!
  
  – pauld
  Mar 23 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The code shown above is simplified to the scope of the original question. The threads used are not thrown away but are long running and draw from a PriorityBlockingQueue one item at a time to process. I definitely see how this could be improved using ExecutorService to manage threads. Currently all the processing steps are encapsulated in ProcessRunnable including multiple IO calls - do you think there would be performance differences from splitting up each step and using CompletableFuture on all IO vs submitting a list of Runnables for the executor service to process/execute?
  
  – pauld
  Mar 23 at 6:02
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also - I know how to use a search engine! Not to be flippant or lazy, just asking if you yourself have found any sources you think explain or show things in a particularly helpful way. You seem to have the creds to where its worth asking the question!
  
  – pauld
  Mar 23 at 6:07
  

  
  
  
  

add a comment | 

2

Here:

runnable -> new Thread(runnable).start()

The key point that actually makes your code multithreaded is that you call the start() method of your thread objects. If you would just call the run method of the thread class, then you actually end up with the "enclosing" thread doing all the work.

Finally, please note that using "bare" threads directly isn't ideal. It is okay to learn about that, but Java offers important abstractions like the ExecutorService that should be used instead for various reasons.

The main reason to avoid raw threads: you have to control all subtle details manually. How many threads should be used? What about pooling and sharing threads (creating a thread comes with a lot of overhead, so in the real world you avoid creating threads for single tasks to then throw them away, like your code does). Beyond that: typically you want to solve a business problem. You want to use multiple threads to prevent bottle neck situations. Examole: you want to make multiple requests over the network in parallel to fetch and process data. Then you really only care about the end result, and not about low level threading subtleties! Then you would for example use Future or CompleteableFuture objects.

Simply use a search engine and research those terms, you will find plenty of material.

share|improve this answer

edited Mar 23 at 5:24

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  thanks for your comment! Would you mind elaborating on the advantages provided by using the ExecutorService and or recommend any reading material that you think is particularly illuminating? The threads are sharing state via BlockingQueues/BlockingDeques - I found it relatively simple to manage / end the threads appropriately based of the the BlocksQueues but of course would love to understand a better way of doing things!
  
  – pauld
  Mar 23 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The code shown above is simplified to the scope of the original question. The threads used are not thrown away but are long running and draw from a PriorityBlockingQueue one item at a time to process. I definitely see how this could be improved using ExecutorService to manage threads. Currently all the processing steps are encapsulated in ProcessRunnable including multiple IO calls - do you think there would be performance differences from splitting up each step and using CompletableFuture on all IO vs submitting a list of Runnables for the executor service to process/execute?
  
  – pauld
  Mar 23 at 6:02
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Also - I know how to use a search engine! Not to be flippant or lazy, just asking if you yourself have found any sources you think explain or show things in a particularly helpful way. You seem to have the creds to where its worth asking the question!
  
  – pauld
  Mar 23 at 6:07
  

  
  
  
  

add a comment | 

Here:

runnable -> new Thread(runnable).start()

The key point that actually makes your code multithreaded is that you call the start() method of your thread objects. If you would just call the run method of the thread class, then you actually end up with the "enclosing" thread doing all the work.

Finally, please note that using "bare" threads directly isn't ideal. It is okay to learn about that, but Java offers important abstractions like the ExecutorService that should be used instead for various reasons.

The main reason to avoid raw threads: you have to control all subtle details manually. How many threads should be used? What about pooling and sharing threads (creating a thread comes with a lot of overhead, so in the real world you avoid creating threads for single tasks to then throw them away, like your code does). Beyond that: typically you want to solve a business problem. You want to use multiple threads to prevent bottle neck situations. Examole: you want to make multiple requests over the network in parallel to fetch and process data. Then you really only care about the end result, and not about low level threading subtleties! Then you would for example use Future or CompleteableFuture objects.

Simply use a search engine and research those terms, you will find plenty of material.

share|improve this answer

edited Mar 23 at 5:24

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

runnable -> new Thread(runnable).start()

share|improve this answer

edited Mar 23 at 5:24

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171

answered Mar 23 at 5:08

GhostCatGhostCat

98.6k1796171