java中的远距离旅行程序

Question

我得到了部分完成的代码来完成，但我不知道下一步该做什么。 该程序要求用户输入以确定行驶距离。
我填写了大部分代码，但我似乎不知道还要添加什么才能使 getDistance() 起作用。 有人可以给我一个建议吗？

说明如下：

车辆行驶的距离可以计算如下： 距离 = 速度 * 时间 例如，如果火车以每小时 40 英里的速度行驶三个小时，则行驶距离为 120 英里。编写一个程序，询问车辆的速度（以英里/小时为单位）和已行驶的小时数。它应该使用循环来显示车辆在用户指定的时间段内每小时行驶的距离。例如，如果一辆车以 40 英里/小时的速度行驶了三个小时，它应该显示类似于以下报告的报告：行驶距离小时

//Distance.java

public class Distance
{
   private double speed;   // The vehicle speed
   private int hours;      // The hours traveled

   /**
    * The constructor initializes the object
    * with a vehicle speed and number hours
    * it has traveled.
    */

   public Distance(double s, int h)
   {

   }

   /**
    * The setSpeed method sets the vehicle's
    * speed.
    */

   public void setSpeed(double s)
   {
       speed = s;
   }

   /**
    * The setHours method sets the number of
    * hours traveled.
    */

   public void setHours(int h)
   {
       hours = h;
   }

   /**
    * The getSpeed method returns the speed
    * of the vehicle.
    */

   public double getSpeed()
   {
       return speed;
   }

   /**
    * The getHours method returns the number
    * of hours traveled by the vehicle.
    */

   public int getHours()
   {
       return hours;
   }

   /**
    * The getDistance method returns the
    * distance traveled by the vehicle.
    */

   public double getDistance()
   {
       return speed * hours;
   }
}



//DistanceDemo.java

public class DistanceDemo
{
   public static void main(String[] args)
   {
      double speed;     // Vehicle's speed
      int maxHours;     // Number of hours
      int period;       // Counter for time periods

      // Create a Scanner object for keyboard input.
      Scanner keyboard = new Scanner(System.in);
  
      // Get the speed.
      System.out.print("Enter the vehicle's speed: ");
      speed = keyboard.nextDouble();
  
      // Validate the speed.
      while (speed < 1)
      {
          System.out.println("Enter a valid speed: ");
          speed = keyboard.nextDouble();
      }
  
      // Get the number of hours.
      System.out.print("Enter the number of hours the " +
                   "vehicle was in motion: ");
      maxHours = keyboard.nextInt();

      // Validate the hours.
      while (maxHours < 1)
      {
         System.out.println("Enter a vaid time");
         maxHours = keyboard.nextInt();
      }
  
      // Display the table header.
      System.out.println("Hour\tDistance Traveled");
      System.out.println("----------------------------------");
  
      // Display the table of distances.
      period = 1;
      while (period <= maxHours)
      {
         // Create a Distance object for this period.
         Distance d = new Distance(speed, period);
     
         // Display the distance for this period.
         System.out.println(period + "\t\t" + d.getDistance());
     
         // Increment period.
         period++;
      }
   }
}

Answer 1

在主函数中，您正在使用构造函数设置速度和小时数。

Distance d = new Distance(speed, period);

但在距离类中，您没有在构造函数中初始化变量速度和小时。

   public Distance(double s, int h)
   {

   }

所以，把这个构造函数写成：

public Distance(double s, int h)
   {
      speed = s;
      hours = h;
   }

Answer 2

需要填写Distance的构造函数来设置速度和小时的值

public Distance(double s, int h) {
  speed = s;
  hours = h;
}

Answer 3

更改距离构造函数以在创建对象期间设置速度和小时数

public Distance(double s, int h)
{
   speed = s;
   hours = h;
}

将距离方法更改为

public double getDistance(int hours)
{
   return speed * hours;
}

然后替换

// Display the table of distances.
  period = 1;
  while (period <= maxHours)
  {
     // Create a Distance object for this period.
     Distance d = new Distance(speed, period);
 
     // Display the distance for this period.
     System.out.println(period + "\t\t" + d.getDistance());
 
     // Increment period.
     period++;
  }

与

Distance d = new Distance(speed,maxHours);
      
      for (int i = 1;i<=maxHours;i++) {
        System.out.println("Hour "+i+" "+"Distance Traveled"+" "+d.getDistance(i));  


     

无需复杂化额外的变量，只需将 getDistance 方法更改为一个小时的参数，因此它会返回某个小时的距离，而 for 循环将小时从 1 更改为当前小时将为您提供准确的结果。