我在使用Java代码时遇到麻烦。我应该在循环中输入“成绩”(我的退出条件是-1),然后将其放入频率表中,问题是我收到此错误:

java.lang.ArrayIndexOutOfBoundsException: -1
    at MakeUp.main(MakeUp.java:36)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at      edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:267)


这是我的代码:

class MakeUp
{
public static void main (String[] args)
{
  int grade[];
  int freq[]=new int [50];
  grade= new int [50];
  int count=0,mark;

  System.out.println("Enter the grades of the class");
  System.out.println("Just enter -1 to end the input");


  do
      {
    System.out.println("Grade " +(count+1)+":");
    mark=In.getInt();
    if (mark>=0)
    {
     grade[count]=mark;
     count=count+1;
    }
  }
  while(mark!=-1);


     for (int i=0; i < grade.length;i++)
      {
     grade[i]=mark;
   }

  if (mark==-1)
  {
  for (int i=0; i<grade.length;i++)
  {
   ++freq[grade[i]];
  }
  System.out.println("Results");

  for (int i=0; i<grade.length;i++)
  {
    System.out.println("Grade " +(i+1) + " = " +grade[i]);
  }

System.out.println("Face\tFrequency\"");
System.out.println("=====================");
  for (int i = 0; i<freq.length; i++)
  {
  System.out.println((i+1)+"\t"+freq[i]);
  }
  }
  }
 }


我不确定是什么问题,并且我尝试更改有问题但无济于事的第35行。任何帮助都感激不尽。谢谢

最佳答案

以下循环用grade值填充您的-1数组(因为mark = -1,这是之前执行的do-while循环的退出条件):

for (int i = 0; i < grade.length; i++) {
            grade[i] = mark;
        }


在这里,任何grade[i] = -1,因此您尝试从freqs数组访问索引-1:

++freq[grade[i]];

10-08 10:47