Identifer expect error

[blknmld69]

I am having a problem getting my program to compile. I recieve the identifier error coming from my array.

 public class GradeCalculator extends JFrame 
   { 
      private static final int WIDTH = 550; 
        private static final int HEIGHT = 430; 
        int gradeCalc; 
        int Student; 
        private StudentList[] = new StudentList [20]; 
        private static final int MAX_NUMBER_OF_STUDENTS = 20; 
 

[jkmyoung]

You haven't named your StudentList array. Really common mistake; I do it all the time.

[blknmld69]

when i name it:

private StudentList[] sList= new StudentList [20];

I get 13 errors instead of the one error i am having:

GradeCalculator .java:13: cannot find symbol
symbol : class StudentList
location: class GradeCalculator
private StudentList[] sList = new StudentList[20];
^
GradeCalculator .java:13: cannot find symbol
symbol : class StudentList
location: class GradeCalculator
private StudentList[] sList = new StudentList[20];
^
GradeCalculator .java:143: int cannot be dereferenced
gradeCalc.Stude ntList[s] = new Student();
^
GradeCalculator .java:143: cannot find symbol
symbol : class Student
location: class GradeCalculator
gradeCalc.Stude ntList[s] = new Student();
^
GradeCalculator .java:145: int cannot be dereferenced
gradeCalc.noOfS tudents =
^
GradeCalculator .java:147: int cannot be dereferenced
gradeCalc.score =
^
GradeCalculator .java:150: int cannot be dereferenced
gradeCalc.getSt udentData(inFil e);
^
GradeCalculator .java:151: int cannot be dereferenced
gradeCalc.displ ayGradeAverage( 0);
^
GradeCalculator .java:187: cannot find symbol
symbol : variable studentList
location: class GradeCalculator
boolean classAvg = studentList[(int) (totalScore / noOfStudents)].getClassAverag e();
^
GradeCalculator .java:188: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
stNameTF.setTex t(StudentList[stName].getFirstName() + " "
^
GradeCalculator .java:189: cannot find symbol
symbol : variable studentList
location: class GradeCalculator
+ studentList[stName].getLastName()) ;
^
GradeCalculator .java:190: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
stAvgTA.setText (""+StudentL ist[(int) (totalScore / 5.0)].getStudentAver age());
^
GradeCalculator .java:191: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
classAvgTA.setT ext(""+StudentL ist[(int) (totalScore / noOfStudents)].getClassAverag e()); }
^
13 errors

[jkmyoung]

So this is supposed to be an integer array? eg
private int StudentList [] = new int [20];
or is it an array of students?
private Student StudentList[] = new Student[20];

[blknmld69]

the project just specifies:

Create a program to enter grades and calculate averages and letter grades.
1. Need a class which will contain:
a. Student Name
b. Student Grades (an array of 3 grades)
c. A constructor that clears the student data (use -1 for unset grades)
d. Accessors (get functions) for each of the above, average, and letter grade
e. Mutators (set functions) for items a, b, c
f. Note that the accessor and mutator for Student grades has to have an argument for the grade index.
2. Need another class which will contain:
a. An Array of Students (1 above)
b. A count of number of students in use
c. Constructor that reads data from a text file and sets up the students
3. You need to create a graphical user interface that allows you to:
a. Read data from file
b. Add new students
c. Process existing students
d. Add test grades
e. Based on a radio button setting display either the average or the letter grade
f. Save modified data to file

[blknmld69]

this is my program:

 import java.util.*;  
   import java.io.*;
   import javax.swing.*; 
   import java.awt.*; 
   import java.awt.event.*; 
 
    public class GradeCalculator extends JFrame 
   { 
      private static final int WIDTH = 550; 
        private static final int HEIGHT = 430; 
        int gradeCalc; 
        int Student; 
       private StudentList[] sList = new StudentList[20]; 
        private static final int MAX_NUMBER_OF_STUDENTS = 20; 
 
                // instance variables 
      private int noOfStudents; 
      private double score, tst1, tst2, tst3; 
      private double  classAvg, stAvg, totalScore; 
      private int displayedStudentIndex = 0; 
      private char ltrGrade; 
      private String stName; 
 
                // This area is for the GUI components 
                // Each item that will be displayed will 
                // have a label and a textfield, (L) and (TF),  
                // respectively. 
      private JLabel stNameL, tst1L, tst2L, tst3L, 
                                        classAvgL, stAvgL, headingL; 
      private JTextField stNameTF, tst1TF, tst2TF, tst3TF; 
      private JTextArea classAvgTA, stAvgTA; 
      private JButton exitB, nextB, prevB, calcGrade; 
 
      private ButtonHandler bHandler; 
 
       public GradeCalculator() 
      { 
         setTitle("Grade Calculator");           // set's the title 
         setSize(WIDTH, HEIGHT);                 // set the window size 
         Container pane = getContentPane();      // get the container 
         pane.setLayout(null);                   // set the container's layout to null 
 
         bHandler = new ButtonHandler();         // instantiate the button event handler 
 
                // instantiate the labels 
         headingL = new JLabel("STUDENT RECORD"); 
         stNameL = new JLabel("Student Name", SwingConstants.RIGHT); 
         tst1L = new JLabel("Test 1", SwingConstants.LEFT); 
         tst2L = new JLabel("Test 2", SwingConstants.LEFT); 
         tst3L = new JLabel("Test 3", SwingConstants.LEFT); 
         stAvgL = new JLabel("Student Average     " 
                                                + "\n"   + "Class Average"); 
                //instantiate the text fields 
         stNameTF = new JTextField(65); 
         tst1TF = new JTextField(10); 
         tst2TF = new JTextField(10); 
         tst3TF = new JTextField(10); 
 
                // instantiate the text area 
         classAvgTA = new JTextArea(6, 20); 
         classAvgTA.setAutoscrolls(true); 
 
                // instantiate the buttons and register the listener 
         exitB = new JButton("Exit"); 
         exitB.addActionListener(bHandler); 
 
         nextB = new JButton("Next"); 
         nextB.addActionListener(bHandler); 
 
         prevB = new JButton("Previous"); 
         prevB.addActionListener(bHandler); 
 
         calcGrade = new JButton("Calc Grade"); 
         calcGrade.addActionListener(bHandler); 
 
                // set the size of the labels, text fields, and buttons 
 
         headingL.setSize(200, 30); 
         stNameL.setSize(100, 30); 
         stNameTF.setSize(100, 30); 
         tst1L.setSize(100, 30); 
         tst1TF.setSize(100, 30); 
         tst2L.setSize(120, 30); 
         tst2TF.setSize(100, 30); 
         tst3L.setSize(100, 30); 
         tst3TF.setSize(100, 30); 
         classAvgTA.setSize(370, 120); 
         calcGrade.setSize(100, 30); 
         prevB.setSize(100, 30);
         nextB.setSize(100, 30); 
         exitB.setSize(100, 30); 
 
                //set the location of the labels, text fields, 
                //and buttons 
         headingL.setLocation(220, 10); 
         stNameL.setLocation(20, 50); 
         stNameTF.setLocation(120, 50); 
         tst1L.setLocation(20, 100); 
         tst1TF.setLocation(120, 100); 
         tst2L.setLocation(300, 50); 
         tst2TF.setLocation(420, 50); 
         tst3L.setLocation(300, 100); 
         tst3TF.setLocation(420, 100); 
         classAvgTA.setLocation(70, 230); 
         prevB.setLocation(120, 370); 
         exitB.setLocation(220, 370); 
         nextB.setLocation(320, 370); 
         calcGrade.setLocation(420, 370); 
 
                //add the labels, text fields, and buttons to the pane 
         pane.add(headingL); 
         pane.add(stNameL); 
         pane.add(stNameTF); 
         pane.add(tst1L); 
         pane.add(tst1TF); 
         pane.add(tst2L); 
         pane.add(tst2TF); 
         pane.add(tst3L); 
         pane.add(classAvgTA); 
         pane.add(calcGrade); 
         pane.add(prevB); 
         pane.add(exitB); 
         pane.add(nextB); 
 
         setVisible(true);         //show the window 
         setDefaultCloseOperation(EXIT_ON_CLOSE); 
         System.exit(0); 
      } 
 
 
 
       public static void main (String [] args)
      { 
         new GradeCalculator(); 
      } 
 
 
 
      Scanner inFile =  
                                new Scanner(new FileReader("AcademicGrades.txt")); 
      {
         for (int s = 0; s < MAX_NUMBER_OF_STUDENTS; s++) 
            gradeCalc.StudentList[s] = new Student(); 
 
         gradeCalc.noOfStudents = 
                        inFile.nextInt();       // get the number of students 
         gradeCalc.score = 
                        inFile.nextDouble();    // get the student's scores 
 
         gradeCalc.getStudentData(inFile); 
         gradeCalc.displayGradeAverage(0); 
      }
 
                        // get the student data from file 
 
 
       public void getStudentData(Scanner inFile) 
      { 
         System.out.println("Grade Calculator is getting information..."); 
         System.out.println("One Moment Please"); 
      } 
       private class ButtonHandler implements ActionListener 
      { 
          public void actionPerformed (ActionEvent e) 
         { 
            if (e.getActionCommand().equals("Previous")) 
               if (displayedStudentIndex > 0) 
                  displayGradeAverage(displayedStudentIndex - 1); 
               else 
                  displayGradeAverage(displayedStudentIndex); 
            else if (e.getActionCommand().equals("Next")) 
               if (displayedStudentIndex + 1 < noOfStudents) 
                  displayGradeAverage(displayedStudentIndex + 1); 
               else 
                  displayGradeAverage(displayedStudentIndex); 
            else if (e.getActionCommand().equals("Calc Grade")) 
               displayGradeAverage(0); 
            else 
               System.exit(0); 
         } 
      } 
 
       public void displayGradeAverage(int stName) 
      { 
         displayedStudentIndex = stName; 
         String strName = ""; 
         boolean classAvg = studentList[(int) (totalScore / noOfStudents)].getClassAverage(); 
         stNameTF.setText(StudentList[stName].getFirstName() + " " 
                                                            + studentList[stName].getLastName());
         stAvgTA.setText(""+StudentList[(int) (totalScore / 5.0)].getStudentAverage());
         classAvgTA.setText(""+StudentList[(int) (totalScore / noOfStudents)].getClassAverage()); }
   }
 

[jkmyoung]

Where is your class for 1.?

1. Need a class which will contain:
a. Student Name
b. Student Grades (an array of 3 grades)
c. A constructor that clears the student data (use -1 for unset grades)
d. Accessors (get functions) for each of the above, average, and letter grade
e. Mutators (set functions) for items a, b, c
f. Note that the accessor and mutator for Student grades has to have an argument for the grade index.
 

[blknmld69]

@jkmyoung
Oh wow, dont have it lol.

[blknmld69]

ok i did that:

 import java.util.*;  
   import java.io.*;
   import javax.swing.*; 
   import java.awt.*; 
   import java.awt.event.*; 
 
 
    public class StudentList 
     { 
      String name;                          // Student's name. 
        double test1, test2, test3;     // Grades on three tests. 
        double getAverage() {              // compute average test grade 
        return (test1 + test2 + test3) / 3; 
      } 
   }
 
 
    public class GradeCalculator extends JFrame 
   { 
      private static final int WIDTH = 550; 
      private static final int HEIGHT = 430; 
      int gradeCalc; 
      int student; 
      private StudentList[] sList = new StudentList[20]; 
 
 
                // instance variables 
      private int noOfStudents; 
      private double score, tst1, tst2, tst3; 
      private double  classAvg, stAvg, totalScore; 
      private int displayedStudentIndex = 0; 
      private char ltrGrade; 
      private String stName; 
 
                // This area is for the GUI components 
                // Each item that will be displayed will 
                // have a label and a textfield, (L) and (TF),  
                // respectively. 
      private JLabel stNameL, tst1L, tst2L, tst3L, 
                                        classAvgL, stAvgL, headingL; 
      private JTextField stNameTF, tst1TF, tst2TF, tst3TF; 
      private JTextArea classAvgTA, stAvgTA; 
      private JButton exitB, nextB, prevB, calcGrade; 
 
      private ButtonHandler bHandler; 
 
       public GradeCalculator() 
      { 
         setTitle("Grade Calculator");           // set's the title 
         setSize(WIDTH, HEIGHT);                 // set the window size 
         Container pane = getContentPane();      // get the container 
         pane.setLayout(null);                   // set the container's layout to null 
 
         bHandler = new ButtonHandler();         // instantiate the button event handler 
 
                // instantiate the labels 
         headingL = new JLabel("STUDENT RECORD"); 
         stNameL = new JLabel("Student Name", SwingConstants.RIGHT); 
         tst1L = new JLabel("Test 1", SwingConstants.LEFT); 
         tst2L = new JLabel("Test 2", SwingConstants.LEFT); 
         tst3L = new JLabel("Test 3", SwingConstants.LEFT); 
         stAvgL = new JLabel("Student Average     " 
                                                + "\n"   + "Class Average"); 
                //instantiate the text fields 
         stNameTF = new JTextField(65); 
         tst1TF = new JTextField(10); 
         tst2TF = new JTextField(10); 
         tst3TF = new JTextField(10); 
 
                // instantiate the text area 
         classAvgTA = new JTextArea(6, 20); 
         classAvgTA.setAutoscrolls(true); 
 
                // instantiate the buttons and register the listener 
         exitB = new JButton("Exit"); 
         exitB.addActionListener(bHandler); 
 
         nextB = new JButton("Next"); 
         nextB.addActionListener(bHandler); 
 
         prevB = new JButton("Previous"); 
         prevB.addActionListener(bHandler); 
 
         calcGrade = new JButton("Calc Grade"); 
         calcGrade.addActionListener(bHandler); 
 
                // set the size of the labels, text fields, and buttons 
 
         headingL.setSize(200, 30); 
         stNameL.setSize(100, 30); 
         stNameTF.setSize(100, 30); 
         tst1L.setSize(100, 30); 
         tst1TF.setSize(100, 30); 
         tst2L.setSize(120, 30); 
         tst2TF.setSize(100, 30); 
         tst3L.setSize(100, 30); 
         tst3TF.setSize(100, 30); 
         classAvgTA.setSize(370, 120); 
         calcGrade.setSize(100, 30); 
         prevB.setSize(100, 30);
         nextB.setSize(100, 30); 
         exitB.setSize(100, 30); 
 
                //set the location of the labels, text fields, 
                //and buttons 
         headingL.setLocation(220, 10); 
         stNameL.setLocation(20, 50); 
         stNameTF.setLocation(120, 50); 
         tst1L.setLocation(20, 100); 
         tst1TF.setLocation(120, 100); 
         tst2L.setLocation(300, 50); 
         tst2TF.setLocation(420, 50); 
         tst3L.setLocation(300, 100); 
         tst3TF.setLocation(420, 100); 
         classAvgTA.setLocation(70, 230); 
         prevB.setLocation(120, 370); 
         exitB.setLocation(220, 370); 
         nextB.setLocation(320, 370); 
         calcGrade.setLocation(420, 370); 
 
                //add the labels, text fields, and buttons to the pane 
         pane.add(headingL); 
         pane.add(stNameL); 
         pane.add(stNameTF); 
         pane.add(tst1L); 
         pane.add(tst1TF); 
         pane.add(tst2L); 
         pane.add(tst2TF); 
         pane.add(tst3L); 
         pane.add(classAvgTA); 
         pane.add(calcGrade); 
         pane.add(prevB); 
         pane.add(exitB); 
         pane.add(nextB); 
 
         setVisible(true);         //show the window 
         setDefaultCloseOperation(EXIT_ON_CLOSE); 
         System.exit(0); 
      } 
 
 
       public static void main (String [] args)
      { 
         new GradeCalculator(); 
      } 
 
      Scanner inFile =  
                                new Scanner(new FileReader("AcademicGrades.txt")); 
      {
         for (int s = 0; s < MAX_NUMBER_OF_STUDENTS; s++) 
            gradeCalc.StudentList[s] = new Student(); 
 
         gradeCalc.noOfStudents = 
                        inFile.nextInt();       // get the number of Students 
         gradeCalc.score = 
                        inFile.nextDouble();    // get the Student's scores 
 
         gradeCalc.getStudentData(inFile); 
         gradeCalc.displayGradeAverage(0); 
      }
 
                        // get the Student data from file 
 
       public void getStudentData(Scanner inFile) 
      { 
         System.out.println("Grade Calculator is getting information..."); 
         System.out.println("One Moment Please"); 
      } 
       private class ButtonHandler implements ActionListener 
      { 
          public void actionPerformed (ActionEvent e) 
         { 
            if (e.getActionCommand().equals("Previous")) 
               if (displayedStudentIndex > 0) 
                  displayGradeAverage(displayedStudentIndex - 1); 
               else 
                  displayGradeAverage(displayedStudentIndex); 
            else if (e.getActionCommand().equals("Next")) 
               if (displayedStudentIndex + 1 < noOfStudents) 
                  displayGradeAverage(displayedStudentIndex + 1); 
               else 
                  displayGradeAverage(displayedStudentIndex); 
            else if (e.getActionCommand().equals("Calc Grade")) 
               displayGradeAverage(0); 
            else 
               System.exit(0); 
         } 
      } 
 
       public void displayGradeAverage(int stName) 
      { 
         displayedStudentIndex = stName; 
         String strName = ""; 
         boolean classAvg = StudentList[(int) (totalScore / noOfStudents)].getClassAverage(); 
         stNameTF.setText(StudentList[stName].getFirstName() + " " 
                                                            + StudentList[stName].getLastName());
         stAvgTA.setText(""+StudentList[(int) (totalScore / 3.0)].getStudentAverage());
         classAvgTA.setText(""+StudentList[(int) (totalScore / noOfStudents)].getClassAverage()); }
   }
 

then i get these error i think its because it illegal but dont know how to fix it.

Errors:

StudentList.jav a:18: class GradeCalculator is public, should be declared in a file named GradeCalculator .java
public class GradeCalculator extends JFrame
^
StudentList.jav a:150: cannot find symbol
symbol : variable MAX_NUMBER_OF_S TUDENTS
location: class GradeCalculator
for (int s = 0; s < MAX_NUMBER_OF_S TUDENTS; s++)
^
StudentList.jav a:151: int cannot be dereferenced
gradeCalc.Stude ntList[s] = new Student();
^
StudentList.jav a:151: cannot find symbol
symbol : class Student
location: class GradeCalculator
gradeCalc.Stude ntList[s] = new Student();
^
StudentList.jav a:153: int cannot be dereferenced
gradeCalc.noOfS tudents =
^
StudentList.jav a:155: int cannot be dereferenced
gradeCalc.score =
^
StudentList.jav a:158: int cannot be dereferenced
gradeCalc.getSt udentData(inFil e);
^
StudentList.jav a:159: int cannot be dereferenced
gradeCalc.displ ayGradeAverage( 0);
^
StudentList.jav a:194: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
boolean classAvg = StudentList[(int) (totalScore / noOfStudents)].getClassAverag e();
^
StudentList.jav a:195: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
stNameTF.setTex t(StudentList[stName].getFirstName() + " "
^
StudentList.jav a:196: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
+ StudentList[stName].getLastName()) ;
^
StudentList.jav a:197: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
stAvgTA.setText (""+StudentL ist[(int) (totalScore / 3.0)].getStudentAver age());
^
StudentList.jav a:198: cannot find symbol
symbol : variable StudentList
location: class GradeCalculator
classAvgTA.setT ext(""+StudentL ist[(int) (totalScore / noOfStudents)].getClassAverag e()); }
^
13 errors

[blknmld69]

I would like to know how can I use the stringValueOf to remove this error:

double cannot be dereferenced
gradeCalc.noOfS tudents = inFile.nextInt( ); // get the number of Students
^
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