import java.io.*;
public class tongji {
    public static void main(String[] args) //throws IOException
    {
     String str1,str2,str3,str4,str5;
     int x=0,z=0,i=0,y=0;
     int a[]=new int[5];
     BufferedReader buf;
     buf=new BufferedReader(new InputStreamReader(System.in));
     System.out.print("输入成绩:");
     str1=buf.readLine();
     a[0]=Integer.parseInt(str1);
     System.out.print("输入成绩:");
     str2=buf.readLine();
     a[1]=Integer.parseInt(str2);
     System.out.print("输入成绩:");
     str3=buf.readLine();
     a[2]=Integer.parseInt(str3);
     System.out.print("输入成绩:");
     str4=buf.readLine();
     a[3]=Integer.parseInt(str4);
     System.out.print("输入成绩:");
     str5=buf.readLine();
     a[4]=Integer.parseInt(str5);
     do
     {
      if (a[i]<0 || a[i]>100)
       //JOptionPane.showMessageDialog(null, "shurucuowu!");
       System.out.print("输入错误!");
      if (a[i]>=0 && a[i]<60)
       x=x+1;
      if (a[i]>=60 && a[i]<=75)
       y=y+1;
      if (a[i]>75 && a[i]<=100)
       z=z+1;
      i++;
     }while(i<5);
     System.out.println("A="+z);
     System.out.println("B="+y);
     System.out.println("C="+x);     
 } 
    
    
}
可以正常运行。但是下面的就不运行
import java.io.*;
public class tongji {
    public static void main(String[] args) //throws IOException
    {
     String str1,str2,str3,str4,str5;
     int x=0,z=0,i=0,y=0;
     int a[]=new int[5];
     BufferedReader buf;
     buf=new BufferedReader(new InputStreamReader(System.in));
     System.out.print("输入成绩:");
     str1=buf.readLine();
     a[0]=Integer.parseInt(str1);
     System.out.print("输入成绩:");
     str2=buf.readLine();
     a[1]=Integer.parseInt(str2);
     System.out.print("输入成绩:");
     str3=buf.readLine();
     a[2]=Integer.parseInt(str3);
     System.out.print("输入成绩:");
     str4=buf.readLine();
     a[3]=Integer.parseInt(str4);
     System.out.print("输入成绩:");
     str5=buf.readLine();
     a[4]=Integer.parseInt(str5);
     while(i<5)
     {
      if (a[i]<0 || a[i]>100)
       System.out.print("输入错误!");
      if (a[i]<60)
       x=x+1;
      if (a[i]>=60 && a[i]<=75)
       y=y+1;
      if (a[i]>75)
       z=z+1;
      i++;
     }
     System.out.println("A="+z);
     System.out.println("B="+y);
     System.out.println("C="+x);     
 } 
    
    
}
   



											
	    

	

