Parallel Computation in Groovy

Parallel.groovy

import java.util.concurrent.*
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.function.Function;

ExecutorService executor = Executors.newFixedThreadPool(2);

def <A> Future<A> run(ExecutorService s, Closure<Future<A>> a) { 
  a(s) 
} 
  
//type Par[A] = ExecutorService => Future[A]
def cls = { ExecutorService s ->
    return executor.submit( new Thread(new CustomThread()) )
}

class CustomThread implements Runnable{
    @Override
    public void run()
    {
        println 'Hello'
    }
}

class FutureCustom<T> implements Future<T> {

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        return false;
    }

    @Override
    public boolean isCancelled() {
        return false;
    }

    @Override
    public boolean isDone() {
        return false;
    }

    @Override
    public T get() throws InterruptedException, ExecutionException {
        return null;
    }

    @Override
    public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        return null;
    }
}

def future = run(executor,cls)
future.get()