Getting grades into a gradebook

[Lisa Smith]

I am trying to create two classes, 1 called Student record and 1 called grade book. In student record I am collecting tha name and grades of the student . In gradebook I'm computing the average and sorting names alphabetically.I have computed the average in Student record because I cannot get gradebook to work. I will cut and paste the code when I get gradebook to work. I am trying to compile grade book but I get this error
C:\javas>c:\j2sdk1.4.1_02\bin\javac GradeBook.java
GradeBook.java:35: cannot resolve symbol
symbol : constructor StudentRecord (java.lang.String,int[])
location: class StudentRecord
table[currentSize] = new StudentRecord(name, grades);
^
1 error
his is my gradebook code:

  
  /*
 * GradeBook.java
 *
 * Created on June 19, 2003, 4:07 PM
 */
/**
 *
 * 
 */
public class GradeBook {
    private final StudentRecord[] table;
    private int currentSize = 0;
    private final int maxSize;
    /**
     * Creates a new instance of Gradebook
     *
     * @param size the number of students in the class
     */
    public GradeBook(final int size) {
        maxSize = size;
        this.table = new StudentRecord[maxSize];
    }
    /**
     * Creates a new student record and inserts it into the gradebook.
     *
     * @param name the name of the student to be added
     * @ param grades an array of grades for the student
     */
    public void insertStudent(final String name, final int[] grades) {
        if (currentSize < maxSize) {
            table[currentSize] = new StudentRecord(name, grades);
            currentSize++;
        }
    }
}

This is studentrecord

/**
 *
 * 
 * 
 * 
 */
  public class StudentRecord
{
  final int arraySize = 25;
  // Private instance varibles
   private final String name;          // student name
   private final int[]  grades;        // grades
  int  Count;    // number of grades per student
  // Constructor
  StudentRecord( String studentName )
  {
    name = studentName  ;
    grades =  new int[ arraySize ] ;
    Count =  0  ;
  }

  public void print ()
  {
    System.out.println ( "Name: " + name  );
    System.out.println( "Grades:");
    for ( int j=0; j < Count ; j++ )
      System.out.println ( "  grade " + j + ": " + grades[ j ] );
  }
  public void addGrade ( int grade )
  {
    if ( Count < arraySize ) 
      grades[Count] = grade ;
    Count ++ ;
  }
  public  int average ( )
  {
    int sum =  0  ;
    for ( int j=0; j < Count; j++ )  
      sum += grades[ j ] ;
    return   sum / Count ;
  }
}
  

[Michael Morris]

You are trying to create a new StudentRecord object with the call to:

table[currentSize] = new StudentRecord(name, grades);

The only constructor you have in the StudentRecord class is:

StudentRecord( String studentName )

So what's a compiler to do? The fix is to provide a constructor that takes a String and int[] thus:

StudentRecord(String studentName, int[] grades)

[Lisa Smith]

I di exactly what you recommended but when I used my test class i recieved this error.
C:\javas>java StudentTest
Exception in thread "main" java.lang.NoSuchMethodError: StudentRecord.<init>(Lja
va/lang/String V
at StudentTest.main(StudentTest.java:7)
Here are my changes!

  
 public class StudentRecord
{
  
    final int arraySize = 25;
  // Private instance varibles
   private final String name;          // student name
   private final int[]  grades;        // grades
  int  Count;    // number of grades per student
  // Constructor
 StudentRecord(String studentName, int[] grades1)
  {
    name = studentName  ;
    grades = new int[arraySize ] ;
   
    Count =  0  ;
  }

   public void print ()
  {
    System.out.println ( "Name: " + name  );
    System.out.println( "Grades:");
    for ( int j=0; j < Count ; j++ )
      System.out.println ( "  grade " + j + ": " + grades[ j ] );
  }
  public void addGrade ( int grade )
  {
    if ( Count < arraySize ) 
      grades[Count] = grade ;
    Count ++ ;
  }
  public  int average ( )
  {
    int sum =  0  ;
    for ( int j=0; j < Count; j++ )  
      sum += grades[ j ] ;
    return   sum / Count ;
  }
  
 }

This is my test code:

 
class StudentTest
{
  public static void main ( String[] args )
  {
     // create a student object
     StudentRecord stud = new StudentRecord( "Nate") ;
     // add a few grades
     stud.addGrade( 90 ) ;
     stud.addGrade( 95 ) ;
     stud.addGrade( 88 ) ;
     stud.addGrade( 78 ) ;
     stud.addGrade( 82 ) ;
     stud.addGrade( 97 ) ;
 StudentRecord stud1 = new StudentRecord( "Yvette" ) ;
     // add a few grades
     stud1.addGrade( 90 ) ;
     stud1.addGrade( 50 ) ;
     stud1.addGrade( 30 ) ;
     stud1.addGrade( 54 ) ;
     stud1.addGrade( 78 ) ;
     stud1.addGrade( 44 ) ;
StudentRecord stud2 = new StudentRecord( "Maria" ) ;
     // add a few grades
     stud2.addGrade( 90 ) ;
     stud2.addGrade( 95 ) ;
     stud2.addGrade( 88 ) ;
     stud2.addGrade( 78 ) ;
     stud2.addGrade( 82 ) ;
     stud2.addGrade( 97 ) ;

     stud.print() ;
     stud1.print() ;
     stud2.print() ;
     
  
     System.out.println( "Average grade for this student is : " + stud.average() );
    
  
}

 

It worked before and know I don't understand why it is not working.

[Michael Morris]

Lisa, I wasn't suggesting that you remove the other constructor. It's OK to have more than one. You still have a problem with the new constructor. Your code completely ignores the int[] array of grades. Let me make a couple of suggestions:

   StudentRecord(String studentName, int[] grades1)  {
    if (grades1.length > arraySize) {
        throw new IllegalArgumentException("Grade array exceeds fixed size");
    }
    name = studentName  ;
    grades = new int[arraySize];
    System.arraycopy(grades1, 0, grades, 0, grades1.length);
    Count =  grades1.length  ;
  }
  
  StudentRecord(String studentName)  {
    //Call the two arg constructor with an empty grade array
    this(studentName, new int[0]);
  }

[ June 26, 2003: Message edited by: Michael Morris ]

[Lisa Smith]

So should I put the same constructor in gradebook?

[Lisa Smith]

I have Student record working again and gradebook compiled. Can you look at grade book and let me know if the Studentrecord is going there. If so how do I sort it alphabetically and print it out?
I tried using util-array sort but I get an error. Should I use a compare method before call array sort.
This is grade book:

 
 /*
 * GradeBook.java
 *
 * Created on June 19, 2003, 4:07 PM
 */
/**
 *
 * 
 */
public class GradeBook {
    private final StudentRecord[] table;
    private int currentSize = 0;
    private final int maxSize;
   
   
    /**
     * Creates a new instance of Gradebook
     *
     * @param size the number of students in the class
     */
    public GradeBook(final int size) {
        maxSize = size;
        this.table = new StudentRecord[maxSize];
     
    }

    /**
     * Creates a new student record and inserts it into the gradebook.
     *
     * @param name the name of the student to be added
     * @ param grades an array of grades for the student
     */
    public void insertStudent(final String name, final int[] grades) {
        if (currentSize < maxSize) {
            table[currentSize] = new StudentRecord(name, grades);
            currentSize++;
        }
  
       }
  // public void sort() {
        // java.util.Arrays.sort(GradeBook);
         
  
}
 

[Michael Morris]

For Arrays.sort() to work, StudentRecord will need to implement the Comparable interface. It has one method:

public int compareTo(Object obj);

It returns a negative int if this is less than obj, a positive int if greater and 0 if equal. Since you want to sort it alphabetically by student name and since string is a Comparable then the method would look something like this:

public int compareTo(Object obj) {
    return this.name.compareTo(((StudentRecord) obj).name);
}

Then your sort() method in GradeBook would look like:

public void sort() {
    Arrays.sort(table);
}

[Lisa Smith]

Thanks I get what you are saying about that. Now my problem is implementing it in StudentTest. Here are my errors
StudentTest.java:42: cannot resolve symbol
symbol : method insertStudent ()
location: class StudentRecord
stud.insertStudent();
^
StudentTest.java:43: cannot resolve symbol
symbol : method insertStudent ()
location: class StudentRecord
stud1.insertStudent();
^
StudentTest.java:44: cannot resolve symbol
symbol : method insertStudent ()
location: class StudentRecord
stud2.insertStudent();
^
StudentTest.java:47: cannot resolve symbol
symbol : variable sort
location: class StudentTest
sort.table();
^
StudentTest.java:49: cannot resolve symbol
symbol : variable table
location: class StudentTest
table.print();
^
I know it has something to do with the methods that I have created, I just don't know what.
My code again
Gradebook

 
/*
 * GradeBook.java
 *
 * Created on June 19, 2003, 4:07 PM
 */
/**
 *
 * 
 */
public class GradeBook {
    private final StudentRecord[] table;
    private int currentSize = 0;
    private final int maxSize;
   
   
    /**
     * Creates a new instance of Gradebook
     *
     * @param size the number of students in the class
     */
    public GradeBook(final int size) {
        maxSize = size;
        this.table = new StudentRecord[maxSize];
     
    }

    /**
     * Creates a new student record and inserts it into the gradebook.
     *
     * @param name the name of the student to be added
     * @ param grades an array of grades for the student
     */
    public void insertStudent(final String name, final int[] grades) {
        if (currentSize < maxSize) {
            table[currentSize] = new StudentRecord(name, grades);
            currentSize++;
        }
  
       }
  
      public void sort() {
         java.util.Arrays.sort(table);

  }
  
}
Student  Record
 

/**
*
*
*
*
*/
public class StudentRecord
{

final int arraySize = 25;
// Private instance varibles
private final String name; // student name
private final int[] grades; // grades
int Count; // number of grades per student
// Constructor
StudentRecord(String studentName, int[] grades1) {
if (grades1.length > arraySize)
{
throw new IllegalArgumentException("Grade array exceeds fixed size");
}
name = studentName ;
grades = new int[arraySize];
System.arraycopy(grades1, 0, grades, 0, grades1.length);
Count = grades1.length ;
} StudentRecord(String studentName)
{
//Call the two arg constructor with an empty grade array
this(studentName, new int[0]); }
public int compareTo(Object obj)
{
return this.name.compareTo(((StudentRecord) obj).name);
}
public void print ()
{
System.out.println ( "Name: " + name );
System.out.println( "Grades:");
for ( int j=0; j < Count ; j++ )
System.out.println ( " grade " + j + ": " + grades[ j ] );
}
public void addGrade ( int grade )
{
if ( Count < arraySize )
grades[Count] = grade ;
Count ++ ;
}
public int average ( )
{
int sum = 0 ;
for ( int j=0; j < Count; j++ )
sum += grades[ j ] ;
return sum / Count ;
}

}
Student Test

[CODE]
class StudentTest
{
public static void main ( String[] args )
{
// create a student object
StudentRecord stud = new StudentRecord( "Nate" ) ;
// add a few grades
stud.addGrade( 90 ) ;
stud.addGrade( 95 ) ;
stud.addGrade( 88 ) ;
stud.addGrade( 78 ) ;
stud.addGrade( 82 ) ;
stud.addGrade( 97 ) ;
StudentRecord stud1 = new StudentRecord( "Yvette" ) ;
// add a few grades
stud1.addGrade( 90 ) ;
stud1.addGrade( 95 ) ;
stud1.addGrade( 88 ) ;
stud1.addGrade( 78 ) ;
stud1.addGrade( 82 ) ;
stud1.addGrade( 97 ) ;
StudentRecord stud2 = new StudentRecord( "Maria" ) ;
// add a few grades
stud2.addGrade( 90 ) ;
stud2.addGrade( 95 ) ;
stud2.addGrade( 88 ) ;
stud2.addGrade( 78 ) ;
stud2.addGrade( 82 ) ;
stud2.addGrade( 97 ) ;

stud.print() ;
stud1.print() ;
stud2.print() ;

stud.insertStudent();
stud1.insertStudent();
stud2.insertStudent();

sort.table();
table.print();
System.out.println( "Average grade: " + stud.average() );
}
}
How can I print this alphabetically after they are averaged?
[CODE]