Calculate weighted average with Java 8 streams

Question

How do I go about calculating weighted mean of a Map where the Integer value is the weight for the Double value to be averaged. eg: Map h

Answer 1

static float weightedMean(List value, List weighted, int n) {
    int sum = 0;
    double numWeight = 0;

    for (int i = 0; i < n; i++) {
        numWeight = numWeight + value.get(i).doubleValue() * weighted.get(i).intValue();
        sum = sum + weighted.get(i).intValue();
    }

    return (float) (numWeight) / sum;
}