在 I/O 中使用 Double.parseDouble( )

Question

我正在尝试编写一个程序，从用户那里获取一系列的五个双精度字符串值，然后尝试使用 Double.parseDouble() 方法将这些字符串转换为双精度字符串。我遇到的麻烦是我必须在下一个“Please enter a number”弹出之前输入两个值。这是我得到的输出：

Please enter a number 1: 4
3
Please enter a number 2: 5
4
Please enter a number 3: 3
4
Please enter a number 4: 5
6
Please enter a number 5: 4
2
The average is: 3.8

这是我的代码：

import java.io.*;
import java.util.Scanner;

public class theman {
    public static void main(String[] args) throws IOException{

    // Variables
        int counter;
        int userEntries = 5;
        double sum = 0;


        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);


    // Creating a new Scanner
        Scanner scanner = new Scanner(System.in);

    // Loop for the five entries    
        for (counter = 1; counter <= userEntries; counter++) {
            String input = "";
            System.out.print("Please enter a number " + counter + ": ");
            input = br.readLine();
            double number = Double.parseDouble(input);
            sum += scanner.nextDouble();
        }   

    // Print statements
        System.out.println("The average is: " + sum / userEntries);


    } // End of method header
} // End of class header

解决此问题的最佳方法是什么？我假设这是因为 sum += scanner.nextDouble(); 但我需要它递增所以我真的不能删除它。

Answer 1

你已经有了双倍的，所以没有必要使用 Scanner.nextDouble()。 nextDouble() 方法将输入的下一个标记扫描为双精度。你应该做的是 sum += number.

Answer 2

这是更新后的代码 -

import java.io.*;
import java.util.Scanner;

public class theman {
    public static void main(String[] args) throws IOException{

    // Variables
    int counter;
    int userEntries = 5;
    double sum = 0;

    // Creating a new Scanner
    Scanner scanner = new Scanner(System.in);

    // Loop for the five entries
    for (counter = 1; counter <= userEntries; counter++) {
         System.out.print("Please enter a number " + counter + ": ");
         sum += scanner.nextDouble();
    }

    // Print statements
    System.out.println("The average is: " + sum / userEntries);


  } // End of method header
} // End of class header

Answer 3

final int userEntries = 2;
Scanner in = new Scanner(System.in);
double sum = 0.0;

for (int counter = 1; counter <= userEntries; ++counter) {
    System.out.printf("Please enter a number %d: ", counter);
    sum += in.nextDouble();
}

System.out.printf("The average is: %.2f%n", sum / userEntries);

在 I/O 中使用 Double.parseDouble( )

Using Double.parseDouble( ) within I/O

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io

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