gradebook.java

java编程代码

import java.util.Scanner;

public class GradeBook
{

    private int numberOfStudents; // Same as studentAverage.length.
    private int numberOfQuizzes; // Same as quizeAverage.length.

    private int[][] grade; //numberOfStudents rows and numberOfQuizzes columns.
    private double[] studentAverage;
    private double[] quizAverage;

    public GradeBook(int[][] a)
    {
        if (a.length == 0 || a[0].length == 0)
        {
            System.out.println("Empty grade records. Aborting.");
            System.exit(0);
        }

        numberOfStudents = a.length;
        numberOfQuizzes = a[0].length;
        fillGrade(a);
        fillStudentAverage( );
        fillQuizAverage( );
    }

    public GradeBook(GradeBook book)
    {
        numberOfStudents = book.numberOfStudents;
        numberOfQuizzes = book.numberOfQuizzes;
        fillGrade(book.grade);
        fillStudentAverage( );
        fillQuizAverage( );
    }
 
    public GradeBook( )
    {
        Scanner keyboard = new Scanner(System.in);

        System.out.println("Enter number of students:");
        numberOfStudents = keyboard.nextInt( );

        System.out.println("Enter number of quizzes:");
        numberOfQuizzes = keyboard.nextInt( );

        grade = new int[numberOfStudents][numberOfQuizzes];

        for (int studentNumber = 1; 
                     studentNumber <= numberOfStudents; studentNumber++)
            for (int quizNumber = 1; 
                            quizNumber <= numberOfQuizzes; quizNumber++)
            {
                System.out.println("Enter score for student number "
                                             + studentNumber);
                System.out.println("on quiz number " + quizNumber);
                grade[studentNumber - 1][quizNumber - 1] =
                                                 keyboard.nextInt( );
            }

        fillStudentAverage( );
        fillQuizAverage( );
    }

    private void fillGrade(int[][] a)
    {
        grade = new int[numberOfStudents][numberOfQuizzes];

        for (int studentNumber = 1; 
                        studentNumber <= numberOfStudents; studentNumber++)
        {
            for (int quizNumber = 1; 
                         quizNumber <= numberOfQuizzes; quizNumber++)
                grade[studentNumber][quizNumber] = 
                                        a[studentNumber][quizNumber];
        }
    }

    /**
      Fills the array studentAverage using the data from the array grade.
    */
    private void fillStudentAverage( )
    {
        studentAverage = new double[numberOfStudents];

        for (int studentNumber = 1; 
                        studentNumber <= numberOfStudents; studentNumber++)
        {//Process one studentNumber:
            double sum = 0;
            for (int quizNumber = 1; 
                         quizNumber <= numberOfQuizzes; quizNumber++)
                sum = sum + grade[studentNumber - 1][quizNumber - 1];
            //sum contains the sum of the quiz scores for student number studentNumber.
            studentAverage[studentNumber - 1] = sum/numberOfQuizzes;
            //Average for student studentNumber is studentAverage[studentNumber - 1]
        }
    }

    /**
      Fills the array quizAverage using the data from the array grade.
    */
    private void fillQuizAverage( )
    {
        quizAverage = new double[numberOfQuizzes];

        for (int quizNumber = 1; quizNumber <= numberOfQuizzes; quizNumber++)
        {//Process one quiz (for all students):
            double sum = 0;
            for (int studentNumber = 1; 
                          studentNumber <= numberOfStudents; studentNumber++)
                sum = sum + grade[studentNumber - 1][quizNumber - 1];
            //sum contains the sum of all student scores on quiz number quizNumber.
            quizAverage[quizNumber - 1] = sum/numberOfStudents;
            //Average for quiz quizNumber is the value of quizAverage[quizNumber - 1]
        }
    }

    public void display( )
    {
        for (int studentNumber = 1; 
                    studentNumber <= numberOfStudents; studentNumber++)

        {//Display for one studentNumber:
            System.out.print("Student " + studentNumber + " Quizzes: ");
            for (int quizNumber = 1; 
                             quizNumber <= numberOfQuizzes; quizNumber++)
              System.out.print(grade[studentNumber - 1][quizNumber - 1] + " ");
            System.out.println(" Ave = " + studentAverage[studentNumber - 1] );
        }

        System.out.println("Quiz averages: ");
        for (int quizNumber = 1; quizNumber <= numberOfQuizzes; quizNumber++)
            System.out.print("Quiz " + quizNumber 
                            + " Ave = " + quizAverage[quizNumber - 1] + " ");
        System.out.println( );
    }
}