int numSamples = 100;
int amountOfData = 1000000;
double[] data = new double[amountOfData];//Data comes from somewhere...
double[] results = new double[numSamples];
//a lot of memory contained inside the FunctionEvaluator class,
//expensive to intialise
FunctionEvaluator fe = new FunctionEvaluator();

for(int i=0; i<numSamples; i++) {
    results[i] = fe.sampleAt(i, data);//very expensive computation
}

int numSamples = 100;
int amountOfData = 1000000;
int N = 10;

double[] data = new double[amountOfData];//Data comes from somewhere...
double[] results = new double[numSamples];
//a lot of memory contained inside the FunctionEvaluator class,
//expensive to intialise
FunctionEvaluator[] fe = new FunctionEvaluator[N];

for(int i=0; i<numSamples; i++) {
    //Somehow add available FunctionEvaluators to an ExecutorService
    //so that N FunctionEvaluators can run in parallel. When a
    //FunctionEvaluator is finished, reset then compute a new sample
    //until numSamples samples have been taken.
}