Java 计算器程序中的用户输入错误

这是我用于计算器程序的代码

package javaapp;
import java.util.Scanner;
public class JavaApp {
public static void main(String args[]){
    Scanner matt = new Scanner("System.in");
    double fnum; 
    double snum; 
    double answer;
    System.out.println("Enter first number: ");
    fnum = matt.nextDouble();
   System.out.println("Enter the Second number: ");
    snum = matt.nextDouble();
    answer = fnum + snum;
    System.out.println(answer);
    }
}

这就是错误：

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:909)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextDouble(Scanner.java:2456)
at javaapp.JavaApp.main(JavaApp.java:10)
Java Result: 1

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从

扫描器的构造函数中删除引号

，这样它就不会试图从

字符串

源读取

Scanner matt = new Scanner(System.in);

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JavaApp.java中的第10行在哪里？@MonadNewb手动计数和从堆栈转储中计数

fnum=matt.nextDouble（）