public class DoubleStream {
public static void main(String[] args) {
List<Double> doubleList = new ArrayList<>();
doubleList.add(1.3);
doubleList.add(2.2);
doubleList.add(3.2);
doubleList.add(4.3);
doubleList.add(5.2);
OptionalDouble average = Arrays.stream(doubleList.toArray(new Double[doubleList.size()])).mapToDouble(Number::doubleValue).average();
System.out.println("平均值:"+average);
//第二种方式
double average1 = doubleList.stream().collect(Collectors.averagingDouble(Double::doubleValue));
System.out.println("平均值:" + average1);