[FIXED] CachedThreadPool vs FixedThreadPool

Issue

I would like to know which to use CachedThreadPool or FixedThreadPool in this particular scenario. When the user logins into the app, a list of addresses will be obtained about 10 addresses. I need to do the following:

1. Convert the address into latitude and longitude for which I am calling a Google API
2. Obtain distance between the above fetched latitude and longitude with user's current location also with the help of a Google API

So, I have created a class GetDistance which implements Runnable. In this class I am first calling the Google API and parsing the response to get respective latitude and longitude and then calling and parsing result of another Google API to get driving distance.

private void getDistanceOfAllAddresses(List<Items> itemsList) {
    ExecutorService exService = newCachedThreadPool(); //Executors.newFixedThreadPool(3);
    for(int i =0; i<itemsList.size(); i++) {
        exService.submit(new GetDistance(i,usersCurrentLocation));
    }
    exService.shutdown();
 
}

I have tried with both CachedThreadPool and FixedThreadPool, time taken is almost the same. I am in favour of CachedThreadPool as it is recommended for small operations, but I have some concerns. Lets assume CachedThreadPool creates 10 threads (worst case) to complete the process (10 items), will it be an issue if my app is running on lower end devices? As number of threads created will also affect the RAM of the device.

I want to know your thoughts and opinions on this. Which is better to use?

Solution

Go with newCachedThreadPool it is better fit for this situation, because your task are small and I/O (network) bound. Which means you should create threads (usually 1.5x ~ 2x times) greater than number of processor cores to get optimum output, but here I guess newCachedThreadPool will manage itself. So, newCachedThreadPool will have less overhead as compared to newFixedThreadPool and will help in your situation.

If you had CPU intensive tasks then newFixedThreadPool could have been a better choice.

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Update

A list of addresses will be obtained about 10 addresses.

If you need only 10 address always, then it doesn't matter, go with newCachedThreadPool. But if you think that number of address can increase then use newFixedThreadPool with number of threads <= 1.5x to 2x times number of cores available.

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From Java docs:

newFixedThreadPool

Creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. At any point, at most nThreads threads will be active processing tasks. If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available. If any thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks. The threads in the pool will exist until it is explicitly shutdown.

newCachedThreadPool

Creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available. These pools will typically improve the performance of programs that execute many short-lived asynchronous tasks. Calls to execute will reuse previously constructed threads if available. If no existing thread is available, a new thread will be created and added to the pool. Threads that have not been used for sixty seconds are terminated and removed from the cache. Thus, a pool that remains idle for long enough will not consume any resources. Note that pools with similar properties but different details (for example, timeout parameters) may be created using ThreadPoolExecutor constructors.

Answered By - user4774371
Answer Checked By - Mary Flores (JavaFixing Volunteer)