Zybooks 一直告诉我扫描仪代码有错误，但应该没问题？

Question

我今晚有一个项目要到期，其中我们应该根据输入的初始速度计算输入的轨迹。我已经完成了代码，但由于扫描仪的原因，它一直无法编译，但它应该可以工作。我在下面附上了我的代码：

public class TrajectoryModelingIntro {

    public static void main(String[] args) {
     Scanner scanner = new Scanner(System.in);
     double degrees;
     double time;
     double distance;
     double intialSpeed;
     
     System.out.println("Enter an intial speed: ");
     initialSpeed = scanner.nextDouble();
     
     for (degrees = 25.00; degrees < 90.00; degrees += 5.00) {
        time = 2 * initialSpeed * Math.sin(Math.toRadians(degrees)) / 9.8;
        distance = initialSpeed * time * Math.cos(Math.toRadians(degrees));
        System.out.format("At angle " + "%.2f" , degrees);
        System.out.format(" projectile travels " + "%.2f", distance);
        System.out.println(" meters");
     }
        
        scanner.close();

    }

}

这是我不断收到的代码错误消息：

TrajectoryModelingIntro.java:10: error: cannot find symbol
     Scanner scnr = new Scanner(System.in);
     ^
  symbol:   class Scanner
  location: class TrajectoryModelingIntro
TrajectoryModelingIntro.java:10: error: cannot find symbol
     Scanner scnr = new Scanner(System.in);
                        ^
  symbol:   class Scanner
  location: class TrajectoryModelingIntro
TrajectoryModelingIntro.java:17: error: cannot find symbol
     initialSpeed = scnr.nextDouble();
     ^
  symbol:   variable initialSpeed
  location: class TrajectoryModelingIntro
TrajectoryModelingIntro.java:20: error: cannot find symbol
        time = 2 * initialSpeed * Math.sin(Math.toRadians(degrees)) / 9.8;
                   ^
  symbol:   variable initialSpeed
  location: class TrajectoryModelingIntro
TrajectoryModelingIntro.java:21: error: cannot find symbol
        distance = initialSpeed * time * Math.cos(Math.toRadians(degrees));
                   ^
  symbol:   variable initialSpeed
  location: class TrajectoryModelingIntro
5 errors

如果大家有任何意见或建议，请告诉我！

Answer 1

我可以看到你有两个主要错误，首先你有一个

double intialSpeed

的拼写错误（应该是

initial

，这是你在循环中使用的）。其次，您错过了

java.util.Scanner

import

，您可以通过使用完全限定的类名来省略它。另外，我强烈建议您在一个语句 and 中声明并赋值以使用

try-with-Resources

，而不是显式关闭您的

Scanner

。最后，您可以将所有输出合并到一个语句中（并且您可能不应该使用

String

与格式化输出连接）。就像，

try (java.util.Scanner scanner = new java.util.Scanner(System.in)) {
    System.out.println("Enter an initial speed: ");
    double initialSpeed = scanner.nextDouble();

    for (double degrees = 25.00; degrees < 90.00; degrees += 5.00) {
        double time = 2 * initialSpeed * Math.sin(Math.toRadians(degrees)) / 9.8;
        double distance = initialSpeed * time * Math.cos(Math.toRadians(degrees));
        System.out.printf("At angle %.2f projectile travels %.2f meters%n",
                degrees, distance);
    }
}