我如何計算在Java中的不同方法我的氣瓶體積

Question

import javax.swing.*; 
import java.text.*; 

public class UG3 { 



    public static void main (String[] arg) { 



      String radius = JOptionPane.showInputDialog("Input Radius"); 
      String height = JOptionPane.showInputDialog("Input Height");// input radius and height. 

     try { // trying to make sure that the user inputs information otherwise it will cancel. 

      int rad = Integer.parseInt(radius); 
      int hei = Integer.parseInt(height); 


      NumberFormat r = NumberFormat.getInstance(); 

      r.setMaximumFractionDigits(2); 
      r.setMinimumFractionDigits(2); 

      JOptionPane.showMessageDialog(null, "The volume of the cylinder is approximately "+ r.format(volume) +"CM^3"); // output results. // Here is the problem " volume " is: "cannot be resolved". 



      int yes = JOptionPane.showConfirmDialog(null, "Would you like to find the volume of a cylinder once more?", "", JOptionPane.YES_NO_OPTION); 

      if(yes == JOptionPane.YES_OPTION) { 
       main(arg); 
      } 

      else { 
       JOptionPane.showMessageDialog(null, "You'r welcome! \n \n Click 'OK' to exit", "Cylinder.", JOptionPane.ERROR_MESSAGE); 
      } 
     } 


     catch (NumberFormatException e) { // cancel. 

      JOptionPane.showMessageDialog(null, "Sorry but you have to enter radius and height to complete the task."); 
     } 




    } //main 

    public static double volume(double radius, double height){ 
     return Math.PI * Math.pow(radius,2) * height; 

    } 

}//Cylinder 

我寫了「評論」，告訴你在哪裏。無論如何，「音量無法解決」爲什麼？ 我是否想要從第一種方法中刪除某些東西？有什麼缺失？不能讓我的頭靠近它。 ：S

Answer 1

radius和height是String變量，但你試圖將它們與int值（例如radius >= 1）進行比較。

如果您要在此處做的所有事情都是爲了確保用戶提供了一些信息，您可以對null和/或空字符串（例如radius != null && radius != ""）進行簡單測試。

*編輯補充做，而*

1. 把DO-而圍繞在try-catch。

2. 使用yes == JOptionPane.YES_OPTION作爲而條件。

3. 擺脫

   if (yes == JOptionPane.YES_OPTION) 
       //.... 
   else 
       //.... 
   

   邏輯。