请，打印总外的循环，它会工作良好！代码：

public class test {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a sequence of numbers to sum up: ");
        double total = 0;
        while (in.hasNextDouble()) {
            double input = in.nextDouble();
            total = total + input;
        }
        System.out.println("The Sum is: " + total);
    }

问题在于： System.out.println("The Sum is: " + total); 如果您只想打印最终金额，则需要在 while 循环。

你的主要问题是你把print语句放在了循环中。
也， in.hasNextDouble() 从键盘输入没有意义；当您从文件或数据库中读取数据时，它非常有用 Scanner 为了一些绳子。您可以使用无限循环（例如。 while(true){...} )并在没有用户输入时中断它。

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a sequence of numbers to sum up, press Enter without any input to exit: ");
        double total = 0;
        while (true) {
            String input = in.nextLine();
            if (input.isBlank()) {
                break;
            }
            total += Double.parseDouble(input);
        }
        System.out.println("The Sum is: " + total);
    }
}

示例运行：

Enter a sequence of numbers to sum up, press Enter without any input to exit: 
10
20
30

The Sum is: 60.0

演示一个 Scanner 对于字符串：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner("10 20 30");
        double total = 0;
        while (in.hasNextDouble()) {
            double input = in.nextDouble();
            total = total + input;
        }
        System.out.println("The Sum is: " + total);
    }
}

输出：

The Sum is: 60.0