在BlueJ中使用Negative Infinity（垂直）斜率

Question

我的代碼中的所有內容終於看起來正確。我只是在棘手的事情上遇到麻煩。

我該如何編寫代碼，以便當我輸入兩點並且斜率爲-infinity時，它被識別並且輸出爲Vertical而非Negative Slope。

例如，正斜率的輸出如下所示：

Enter the x and y coordinates of the first point: 3 -2 
Enter the x and y coordinates of the second point: 9 2 
Distance: 7.211 
Positive Slope 

和垂直會是什麼樣子：

Enter the x and y coordinates of the first point: 4 5 
Enter the x and y coordinates of the second point: 4 -3 
Distance: 8.000 
Vertical 

而現在我的垂直輸出的樣子：

Enter the x and y coordinates of the first point: 4 5 
Enter the x and y coordinates of the second point: 4 -3 
Distance: 8.000 
Negative Slope 

以下是我現在的代碼：

import java.util.Scanner; 

public class LineEvaluator 
{ 

    public static void main(String[] args) 
    { 
     Scanner input = new Scanner(System.in); 

     System.out.print("Enter the x and y coordinates of the first point: "); 
     double x1 = input.nextDouble(); 
     double y1 = input.nextDouble(); 

     System.out.print("Enter the x and y coordinates of the second point: "); 
     double x2 = input.nextDouble(); 
     double y2 = input.nextDouble(); 

     double distance = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); 
     System.out.printf("Distance: %.3f", distance); 

     double slope = ((y2 - y1)/(x2 - x1)); 

     if(slope > 0) 
     System.out.println("Positive Slope"); 
     else if(slope < 0) 
     System.out.println("Negative Slope"); 
     else if(slope == 0) 
     System.out.println("Horizontal"); 
    } 
    } 

Answer 1

您可以明確檢查是否slope == Double.NEGATIVE_INFINITY。您應該對Double.POSITIVE_INFINITY執行相同操作。

if (slope == Double.NEGATIVE_INFINITY || slope == Double.POSITIVE_INFINITY) 
     System.out.println("Vertical"); 
    else if(slope > 0) 
     System.out.println("Positive Slope"); 
    else if(slope < 0) 
     System.out.println("Negative Slope"); 
    else if(slope == 0) 
     System.out.println("Horizontal"); 

或者你可以使用Double.isInfinite：

if (Double.isInfinite(slope)) 
     System.out.println("Vertical"); 
    else if(slope > 0) 
     System.out.println("Positive Slope"); 
    else if(slope < 0) 
     System.out.println("Negative Slope"); 
    else if(slope == 0) 
     System.out.println("Horizontal");