Return results from executor in java

(This answer was provided when the question was at revision 1. The OP is editing the question in response to the answer, which makes the answer make less sense - rather than me try to keep up with the edits, please refer to revision 1 to see what this was all responding to...)

If you use Callable instead of Runnable, you can use the future returned by the executor to get the return value. If you just want the probabilities, you could use a Callable<Double> like this:

List<Future<Double>> futures = new ArrayList<>();
for (int i = 0; i < 10; i++) {
    double p1 = Math.pow(2, i);
    for (int j = 5; j < 15; j++) {
        double p2 = Math.pow(2, j);
        Callable<Double> worker = new ProbabilityCalculator(p1, p2);
        futures.add(executor.submit(worker));           
    }
}
// Do whatever else you want to here...

// Now wait for the results and handle them appropriately.
// Note the exceptions that can be thrown...
for (Future<Double> future : futures) {
    double value = future.get();
    ...
}

The important thing here is that a Runnable doesn't return a value, whereas a Callable does.

As it sounds like you need the p1 and p2 values as well, you should probably encapsulate that in a result type, so you'd implement Callable<ProbabilityResult>, e.g.

public class ProbabilityCalculator implements Callable<ProbabilityResult> {
    private final double p1, p2;

    public ProbabilityCalculator(double p1, double p2) {
        this.p1 = p1;
        this.p2 = p2;
    }

    public ProbabilityResult call() {
        double probabilty = ...;
        return new ProbabilityResult(p1, p2, probability);
    }
}

(Where ProbabilityResult would just be a simple data transfer class, effectively - you could just use a double[] with three values, but that would be fairly unpleasant...)

Now you can use:

double bestProbability = -1;
double bestP1 = 0, bestP2 = 0;
for (Future<ProbabilityResult> future : futures) {
    ProbabilityResult result = future.get();
    if (result.getProbability() > bestProbability) {
        bestProbability = result.getProbability();
        bestP1 = result.getP1();
        bestP2 = result.getP2();
    }
}

Note that I've changed WorkerThread to ProbabilityCalculator - you should not be creating an instance of a subclass of Thread here; the point is for the executor to handle the actual threading; you just provide it the tasks to execute. If your WorkerThread class doesn't actually extend Thread, you should rename it to something less misleading.