浮动类型。 而且，

Question

I wrote this code: For each line, it should take the weighted average of these numbers with weights 0.2, 0.4, and 0.4, and it should print out the averaged value on a seperate line on the standard output. For example, for the input below

45.00 67.00 98.00
89.00 23.00 89.00

it should produce

75.00
62.60

It works when i write, for example 45,6 but it doesn't when i write 45.6. This is my code:

import java.util.Scanner;

public class paket {
   public static void main (String [] args){
       Scanner input=new Scanner(System.in);
       float num1,num2,num3,result;

       while(input.hasNext()){

            num1=input.nextFloat();
            num2=input.nextFloat();
            num3=input.nextFloat();

            result= (float) (num1*0.2+num2*0.4+num3*0.4);

            System.out.println("Result is  " +result);
       }
   }
} 

Answer 1

在解析数字之前更改您的语言环境：

Locale.setDefault(new Locale("en", "US"));

Answer 2

A Scanner relies on a Locale to decide how to interpret its input. As other comments have noted, you're running on a system that assumes ',' is the decimal-point, rather than '.'

You can change the Locale your 'input' Scanner uses with

input.useLocale(Locale.US);

to have it interpret floats as using '.' for the decimal point.

You can set it back to your system's default with

input.reset();

Answer 3

You should use the locale when parsing, this way you support both . and , depending on what the user have chosen:

NumberFormat format = NumberFormat.getInstance(Locale.getDefault());      
Number number = format.parse("1,234");   
double d = number.doubleValue();