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伙计们我从读取文件中的数据时遇到问题。从文件问题读取数据(Java初学者语言)
当我试图从文件输入后计算GPA时,我只能得到名称和ID的权利。检查全码here
Name: Ali Ahmad
ID: 2009000
Exception in thread "main" java.lang.NullPointerException
at IcsProject.display(IcsProject.java:136)
at IcsProject.main(IcsProject.java:45)
`
我真的需要这方面的帮助。我花了几个小时来修复它,但我不能。
public static void readFromFile() throws IOException
{
System.out.println("Enter the file name ");
String FileNameInput = keyboard.next();
Scanner filein = new Scanner(new FileInputStream(FileNameInput));
stuName = filein.nextLine();
ID = filein.nextInt();
filein.next();
semNum = filein.nextInt();
courseCode=new String[semNum][];
creditHours=new int[semNum][];
grade=new String[semNum][];
semCode=new int[semNum];
for(int i = 0; i < semNum; i++)
{
semCode[i] = filein.nextInt();
filein.next();
semCourses = filein.nextInt();
for(int j = 0; j < semCourses; j++)
{
courseCode[i][j]=filein.next();
creditHours[i][j]=filein.nextInt();
grade[i][j]=filein.next();
}
}
}
输入数据是这样的:
Ali Ahmad
2009000
Semesters 2
093
Courses 2
IAS100 2 A+
PE100 2 B
101
Courses 4
ICS103 3 A+
MATH101 4 B
PHYS101 4 C+
CHEM101 4 D+
这是该方法计算GPA等能正常工作,手动输入。
public static void display(PrintWriter output)
{
output.println("Name: "+stuName);
output.println("ID: "+ID);
output.println("");
GPA=new double[semNum];
for(int i=0;i<semNum;i++)
{
GPA[i]=0.0;
double creditHoursSum=0.0;
for(int j=0;j<courseCode[i].length;j++)
{
GPA[i]+=creditHours[i][j]*gradeValue(grade[i][j]);
creditHoursSum+=creditHours[i][j];
}
GPA[i]=GPA[i]/creditHoursSum;
}
cumulativeGPA=0.0;
for(int i=0;i<semNum;i++)
cumulativeGPA+=GPA[i];
cumulativeGPA=cumulativeGPA/semNum;
for(int i=0 ; i < semNum ; i++)
output.printf("GPA for semester %d = %.2f\t%s\n",semCode[i],GPA[i],gpaLvl(GPA[i]));//Using `Printf` To limit the number of digits of the GPA. I learned the method from our Course Book.Took me a while to get it though.
output.printf("\nCumulative GPA = %.2f\n",cumulativeGPA);
output.println("");
}
谢谢。我得到这个'名称:阿里·艾哈迈德· ID:2009000 累积GPA = NaN'应该显示像这样'名称:阿里·艾哈迈德· ID:2009000 GPA为093学期= 3.50其次荣誉 GPA的学期101 = 2.67 Good Standing 累积GPA = 2.84' – 2011-05-29 09:27:28
@MohammadFadin您应该向我们展示'display'方法的代码和计算'累积GPA'的代码。 – Howard 2011-05-29 09:29:00
@霍华德我刚刚发布了它。我还在问题开始时发布了完整代码的链接。 – 2011-05-29 09:32:45