java - Java 将 int 转换为 double

Question

我的代码当前遇到问题。 我必须将小时和分钟声明为int，将totalTimeHours声明为double。 TotalTimeHours 用于存储总时间(以小时为单位)，例如 6.555 小时。 我正在解决的问题需要在几小时和几分钟内找到答案， 例如。 6小时36分钟。 对于我的最后一次运行，我需要使用 14.7 加仑的汽油和 359.5 加仑的距离。 我使用 hours = (int)totalTimeHours 来提取整数 6 我应该找到剩余的时间并将其乘以 60 得出分钟数， 但这就是我遇到的阻碍。

下面是我的代码:

  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

替换:

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

与:

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

或

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

Math中有两种方法

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

您传递了一个双参数，因此您调用返回 long 的参数并将其分配给 int ，这是错误的。