Java InputMismatchException錯誤

Question

我已經給了一個任務來進行一些從ft到cm的轉換。我已經完成了大部分工作，並且轉換工作正常。我還想包括A negative number...或A non-digit...的聲明，當我鍵入一個字符串，例如或一個負數，顯示所述消息。

我得到的問題是，當我輸入一個字符串或負數時，例如，當輸入時，得到輸出testProgram.NegativeNumberException。例如testProgram.NonDigitNumberException，當我輸入joe時。

我在想catch有什麼問題，但不確定它在哪裏不會點擊。

package testProgram; 
import java.util.InputMismatchException; 
import java.util.Scanner; 

public class conversion{ 

    public static void main(String[] args) { 
     Scanner scan = new Scanner(System.in); 
     double cm = -1; 
     while(cm == -1){ 
     cm = convertToCentimeters(scan); 

     if(cm!=-1){ 
     System.out.println("Your result = " +cm); 
     } 
     else{ 
      System.out.println("Please enter the values again."); 
     } 
     scan.nextLine(); 
     } 
    } 
    public static double convertToCentimeters(Scanner scan){ 
     double centimeters = -1; 
     try{ 
      double foot = getFootValue(scan); 
      double inch = getInchValue(scan); 
      double totalInches = foot * 12 + inch; 
      centimeters = totalInches * 2.54; 

      }catch(NegativeNumberException e1){ 
       System.out.println(e1); 
      } 
      catch(NonDigitNumberException e2){ 
       System.out.println(e2); 
      } 
      return centimeters; 
    } 
    public static double getFootValue(Scanner scan) throws NegativeNumberException, NonDigitNumberException{ 
     try{ 
     System.out.println("Enter the foot value: "); 
     double foot = scan.nextDouble(); 
     if(foot <= 0){ 
      throw new NegativeNumberException ("A negative foot value has been entered."); 
     } 
     return foot; 
     } 
     catch(InputMismatchException e){ 
      throw new NonDigitNumberException ("A non-digit foot value has been entered."); 
     } 
    } 
    public static double getInchValue(Scanner scan)throws NegativeNumberException, NonDigitNumberException{ 
    try{ 
     System.out.println("Enter the inch value: "); 
     double inch = scan.nextDouble(); 
     if(inch <= 0){ 
      throw new NegativeNumberException ("A negative inch value has been entered."); 
     } 
     return inch; 
     } 
     catch(InputMismatchException e){ 
      throw new NonDigitNumberException ("A non-digit inch value has been entered."); 
     } 
    } 
} 

Answer 1

或者改爲@可怕的建議，你可以在構造函數的自定義異常添加爲 -

NegativeNumberException(String str) { 
    System.out.println(str); 
} 

這將幫助您打印的消息，當您

throw new NegativeNumberException ("A n....");