Tuesday, November 9, 2010

Executor Completion Service

Scenario: you want to load the tasks in parallel and then wait for the completion of all the tasks.

//Callable is different from Runnable that it returns result
private final class StringTask extends Callable<String>{
public String call(){
//Long operations
return "Run";

ExecutorService threadPool = Executors.newFixedThreadPool(4);
CompletionService<String> pool = new ExecutorCompletionService<String>(threadPool);

for(int i = 0; i < 10; i++){
pool.submit(new StringTask());

//you have the result in the order they are completed and you don’t have to keep a
//collection of Future
for(int i = 0; i < 10; i++){
String result = pool.take().get();

//Compute the result

See: Java Concurrency: Executors and Thread Pools

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