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titaniumdecoy · Dec 1st, 2006, 9:58 PM

Grades[] data = new Grades[NUM_PERSON];

This code creates an array capable of storing NUM_PERSON Grades objects. By default, each index is initialized to null.

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data[index].setGrades(firstName, lastName, classNum, grade);

You are attempting to call the method setGrades on null, hence the NullPointerException.

One solution is to initialize each index of data to a new instance of Grades in the GradeReader class' constructor, which will be called when a new instance of GradeReader is created:

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public class GradeReader {

      public GradeReader() {
            for (int i = 0; i < NUM_PERSON; i++)
                  data[i] = new Grades();
      }

...

Dec 1st, 2006, 9:58 PM	#2
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 843 Rep Power: 3	(Toggle Plain Text) Grades[] data = new Grades[NUM_PERSON]; Grades[] data = new Grades[NUM_PERSON]; This code creates an array capable of storing NUM_PERSON Grades objects. By default, each index is initialized to null. (Toggle Plain Text) data[index].setGrades(firstName, lastName, classNum, grade); data[index].setGrades(firstName, lastName, classNum, grade); You are attempting to call the method setGrades on null, hence the NullPointerException. One solution is to initialize each index of data to a new instance of Grades in the GradeReader class' constructor, which will be called when a new instance of GradeReader is created: (Toggle Plain Text) public class GradeReader { public GradeReader() { for (int i = 0; i < NUM_PERSON; i++) data[i] = new Grades(); } ... public class GradeReader { public GradeReader() { for (int i = 0; i < NUM_PERSON; i++) data[i] = new Grades(); } ...