將int轉換為double Java

Question

我的代碼目前有問題。 我必須將小時和分鍾聲明為int，將totalTimeHours聲明為double。 totalTimeHours用於存儲以小時為單位的總時間，例如6.555小時。 例如，我正在處理的問題需要在幾小時和幾分鍾內找到答案。 6小時36分鍾。 對於我的最后一次運行，我需要使用14.7加侖汽油和359.5加侖汽油。 我使用小時=（int）totalTimeHours提取整數6，並應該找到剩余的剩余時間，然后將其乘以60以找到分鍾，但這就是我要堅持的時間。

下面是我的代碼：

  public static void computeMilesPerGallon()
  {   //start brackett for computeMilesPerGallon

     double gallons, distance, mpg, totalTimeHours;   //totalTimeHours is the total  time in just hours
                                                                         //for example totalTimeHours = 6.5555 hrs
     int minutes, hours;
     final String DASHES = "-----------------------------------------------";
     final double AVERAGE_SPEED = 54.5;     

     DecimalFormat oneDecimalDigits = new DecimalFormat ("0.0");   //prints decimal to 1 places
     DecimalFormat threeDecimalDigits = new DecimalFormat ("0.000");   //prints decimal to 3 places  

     System.out.println ("\n\t\t\tSpeed Problem");
     System.out.println ("\t\t\t-------------");
     System.out.print ("\n\t\tEnter in the gallons of gas used: ");   //gets gallons of gas used
     gallons = scan.nextDouble();

     System.out.print ("\t\tEnter in the total distance driven: ");   //gets total distance driven
     distance = scan.nextDouble();

     mpg = distance / gallons;   //calculates mpg
     System.out.println ("\t\tThis is your miles per gallon (mpg): " + oneDecimalDigits.format(mpg));  
                                                                         //displays mpg
    //calculates time// 
     totalTimeHours = distance / AVERAGE_SPEED;

    //below line displays total time in hours to 3 decimal places
     System.out.println ("\n\t\tThis is was your time in hours: " 
                                        + threeDecimalDigits.format(totalTimeHours));

    //extracts hours from time in hours
     hours = (int)totalTimeHours;
        minutes = Math.round((totalTimeHours - hours) * 60);

    //prints total time in hrs and minutes
     System.out.println ("\t\tThis is the total time in hours and minutes: " + hours 
                                            + " hours and " + minutes + " minutes");  

     System.out.println ("\t" + DASHES);

  }

Answer 1

更換 ：

minutes = Math.round((totalTimeHours - hours) * 60);

與 ：

minutes = Math.round((float)((totalTimeHours - hours) * 60));

要么

minutes = (int)Math.round((totalTimeHours - hours) * 60);

數學中有兩種方法

long Math.round(double);
int Math.round(float);

您傳入了double參數，因此您調用了返回long的參數，並將其分配給int，那是錯誤的。

Answer 2

我沒有閱讀所有代碼，但這應該可以解決您在文字中描述的問題：

    double dTime = 6.555;
    int hours = (int) dTime;
    int minutes = (int) ((dTime - hours) * 60);
    System.out.println(hours + ":" + minutes); // prints 6:33