如何解決NaN錯誤

Question

這是計算平均值的代碼，當我運行我的項目時，我收到NaN錯誤

public  static double calculateAverage(){
    double attendence = 0;
    int no_of_matches = 0;
    double average =0;
        for (Team t: ApplicationModel.getTeamList()){
        for(Match m : ApplicationModel.getMatchList()){
                if(m.getTeamname().equals(t.getName())){
                    attendence =+ (m.getAttendence());
                    no_of_matches ++;   
                }
            }
            average = attendence / no_of_matches ;
    } 
        return average;
}

這是調用計算平均方法的代碼

String[] columnNames = {"Name","Coaches","League","Division","Fulltime","Number of Coaches","Average Attendence"};

 if (ApplicationModel.getTeamList()!=null){
     int arrayIndex=0;
     for (Team c :ApplicationModel.getTeamList()){
           String[] currentRow = new String[7];
           currentRow[0] = c.getNameAsString();
           currentRow[1] = c.getCoachesAsString();
           currentRow[2] = c.getLeague();
           currentRow[3] = c.getDivision();
           currentRow[4] = c.getFulltime();
           currentRow[5] = Integer.toString(c.getCoaches().length);
           currentRow[6] = Double.toString(c.calculateAverage());
           rowInfo[arrayIndex]=currentRow;
           arrayIndex++;
           teamDisplay.append(c.toString());
         }
        }

Answer 1

我認為問題可能是這行代碼：

attendence =+ (m.getAttendence());

您可以將總變量分配給值，而不是將值添加到總變量中。 另一個問題是你沒有處理no_of_matches （在命名約定方面是一個可怕的變量名）為0 ，即沒有匹配。 最后， average = attendence / no_of_matches總是重新分配average ，從而丟棄前一個團隊的任何結果。

代碼建議：

double attendence = 0;
int matches = 0;
for (Team t: ApplicationModel.getTeamList())
{
    for(Match m : ApplicationModel.getMatchList())
    {
        if(m.getTeamname().equals(t.getName()))
        {
            attendence += (m.getAttendence());
            matches++;
        }
    }
} 
return matches > 0 ? attendence / matches : 0D;

Answer 2

我認為如果在分割操作中使用no_of_matches > 0之前你可以修復NAN錯誤檢查。

public static double calculateAverage(){
    double attendence = 0;
    int no_of_matches = 0;
    double average = 0;

    for (Team t: ApplicationModel.getTeamList()) {
        for (Match m: ApplicationModel.getMatchList()) {
            if (m.getTeamname().equals(t.getName())) {
                attendence =+ (m.getAttendence());
                no_of_matches ++;   
            }
        }

        if (no_of_matches > 0)
            average = attendence / no_of_matches ;
    }

    return average;
}

附加說明，當您添加此檢查並且no_of_matches為0您的平均值將為0，這意味着您沒有匹配項。

希望這可以幫助。