java运算符/未定义参数类型float,可选<float>
我是Java语言新手,我试图计算加权平均值:
import java.util.ArrayList;
import java.util.Optional;
import java.util.Scanner;
public class App {
public static void main(String[] args) throws Exception {
Scanner keyboard = new Scanner(System.in);
ArrayList<Float> grades = new ArrayList<Float>();
ArrayList<Float> wheightes = new ArrayList<Float>();
int count = 0;
while(count < 3) {
float grade = keyboard.nextFloat();
grades.add(grade);
count += 1;
}
System.out.println("Digite 1 para média ponderada e 2 para aritmética");
int whichAverage = keyboard.nextInt();
switch(whichAverage){
case 1:
float average = 0;
for (int i = 0; i < grades.size(); i++) {
average += grades.get(i);
}
System.out.println("A média aritmética é " + average / grades.size());
case 2:
System.out.println("Informe os 3 pesos:");
float weightedAverage = 0;
for (int i = 0; i < 3; i++) {
float wheight = keyboard.nextFloat();
wheightes.add(wheight);
weightedAverage += grades.get(i) * wheightes.get(i);
}
Optional<Float> sumOfWheightes = wheightes.stream().reduce((prev, next) -> prev + next);
System.out.println("A média ponderada é " + weightedAverage / sumOfWheightes);
default:
System.out.println("Digite 1 ou 2");
}
keyboard.close();
}
}
我试着做了一个简化:
Optional<Float> sumOfWheightes = wheightes.stream().reduce((prev, next) -> prev + next);
然后我尝试将Optional<Float>
除以浮点类型:
System.out.println("A média ponderada é " + weightedAverage / sumOfWheightes);
错误是:
The operator / is undefined for the argument type(s) float, Optional<Float>
我该怎么做这个部门
# 1 楼答案
这个错误真的说明了一切——你不能把一个
float
除以一个Optioanl<Float>
,你需要先把它转换成一个float
。例如,通过使用orElse
: