Question

这是用于计算平均值的代码，当我运行项目时，我收到NaN错误

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;
}

这是调用计算平均方法的代码

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

我认为问题可能就是这行代码：

attendence =+ (m.getAttendence());

不是将值添加到总变量，而是将总变量赋值给该值。另一个问题是你没有处理no_of_matches（在命名约定方面是一个可怕的变量名）是0的情况，即没有匹配。最后，average = attendence / no_of_matches始终重新分配average，从而放弃之前团队的任何结果。

代码建议：

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

我认为您可以在分区操作中使用之前修复NAN错误检查no_of_matches > 0。

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;
}

附加说明，当您添加此项检查且no_of_matches为0时，您的平均值为0，表示您没有匹配。

希望这有帮助。

如何解决NaN错误

2 个答案: