Java8: “Translate” old ForEach Method into Lambda/Stream

Question

after hours of hopeless search, I decided to create a question. I really didn't find anything how I can transform this old fashioned way of coding to stream/lambda .

Maybe there is someone, who can explain it to me. Thanks.

public double getSum() {
    double sum = 0;
    for (Product product : productList) {
        sum += product.getPrice();
    }
    return sum;
}

Answer 1

你可以使用以下内容：

double sum = productList.stream().mapToDouble(product -> product.getPrice()).sum();