java - I don't know where my String index out of range: 0 error is coming from -

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i'm trying take data out of txt file , create comparable objects out of data , add them array. after array created, want make 2d array stores 1 in slot if 2 options meet requirements. keep getting string index out of range: 0 error though , not know comes from. 

 import java.util.*; import java.io.*;  public class coursescheduler {  public int numberofcourses; public int[][] adjacent; public course[] courses;  public coursescheduler(string filename) {   file file = new file(filename);    try{      scanner scan = new scanner(file);      numberofcourses = scan.nextint();      courses = new course[numberofcourses];      adjacent = new int[numberofcourses][numberofcourses];       scan.usedelimiter(",|\\n");      for(int = 0; < numberofcourses;i ++){         if(scan.hasnext()){            string dept = scan.next();            string num = scan.next();            string building = scan.next();            string room = scan.next();            string instruct = scan.next();             courses[i] = new course(dept, num, building, room, instruct);         }      }   }      catch(filenotfoundexception ex){      system.out.println("file not found");   }     for(int x = 0;x<numberofcourses;x++){      for(int y = 0;y<numberofcourses;y++){         adjacent[x][y] = (courses[x].compare(courses[y]));      }   }

}

this code main class

public class course{  string department; string coursenum; string buildingcode; string roomcode; string instructorname;  public course(string dept, string number, string building, string room,    string instructor){   department = dept;   coursenum = number;   buildingcode = building;   roomcode = room;   instructorname = instructor;    }     public string getdept(){   return department;   }   public string getcourse(){   return coursenum;  }   public string getbuilding(){   return buildingcode;  }   public string getroom(){   return roomcode;  }   public string getinstructor(){   return instructorname;  }   public string tostring(){   return department + ";" + coursenum + ";" + buildingcode + ";" + roomcode    + ";" + instructorname;   }    public int compare(course comp){   int ans = 1;   string compnum = comp.getcourse();    if(instructorname == comp.getinstructor())      ans = 0;    if(buildingcode == comp.getbuilding()){      if(roomcode == comp.getroom())         ans = 0;   }   if(department == comp.getdept()){      if(coursenum.charat(0) == compnum.charat(0))         ans = 0;   }    return ans; } }

this code course class

educated guess: error coming line:

 if(coursenum.charat(0) == compnum.charat(0))     ans = 0;

either coursenum or compnum empty.


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