SerialTest.java

/*
    SerialTest.java
    CIS 260
    David Klick
    2006-01-25

This program demonstrates how objects may be directly
    written to and read from a file by implementing the
    Serializable interface.
*/

import java.io.*;

class Student implements Serializable {
    private String lastName;
    private String firstName;
    private int id;
    private double gpa;

Student() { this("", "", 0, 0.0); }
    Student(String lname, String fname, int id, double gpa) {
        setFirstName(lname);
        setLastName(fname);
        setID(id);
        setGPA(gpa);
    }
    public void setFirstName(String fname) { firstName = (fname==null) ? "" : fname; }
    public void setLastName(String lname) { lastName = (lname==null) ? "" : lname; }
    public void setID(int id) { this.id = id; }
    public void setGPA(double gpa) { this.gpa = (gpa>=0) ? gpa : 0; }
    public String getFirstName() { return firstName; }
    public String getLastName() { return lastName; }
    public int getID() { return id; }
    public double getGPA() { return gpa; }
    public String toString() {
        return id + ": " + lastName + ", " + firstName + " ("
            + gpa + ")";
    }
}

public class SerialTest {
    private static ObjectOutputStream ofile;
    private static ObjectInputStream ifile;

public static void main(String[] args) {
        // create and write file
        openOutputFile("student.ser");
        addStudents();
        closeOutputFile();

// read and display file
        openInputFile("student.ser");
        displayStudents();
        closeInputFile();
    }

private static void openOutputFile(String filename) {
        try {
            ofile = new ObjectOutputStream(new FileOutputStream(filename));
        } catch (Exception e) {
            System.err.println("Error opening file.");
            System.exit(3);
        }
    }

private static void addStudents() {
        Student[] st = new Student[5];
        st[0] = new Student("Dave", "Klick", 16, 2.4);
        st[1] = new Student("Susan", "Shilling", 3254, 3.8);
        st[2] = new Student("Barb", "Burpee", 278, 2.9);
        st[3] = new Student("Ken", "Kettlebottom", 90, 3.4);
        st[4] = new Student("Tangwa", "Crangor", 421, 3.9);
        for (int i=0; i<st.length; i++) {
            try {
                ofile.writeObject(st[i]);
            } catch (IOException e) {
                System.err.println("Error writing to file.");
                System.exit(4);
            }
        }
    }

private static void closeOutputFile() {
        try {
            if (ofile != null) ofile.close();
        } catch (Exception e) {
            System.out.println("Error closing file.");
            System.exit(1);
        }
    }

private static void closeInputFile() {
        try {
            if (ifile != null) ifile.close();
        } catch (Exception e) {
            System.out.println("Error closing file.");
            System.exit(2);
        }
    }

private static void openInputFile(String filename) {
        try {
            ifile = new ObjectInputStream(new FileInputStream(filename));
        } catch (Exception e) {
            System.err.println("Error opening file.");
            System.exit(5);
        }
    }

private static void displayStudents() {
        int recnum = 0;

while (true) {
            try {
                Student s = (Student) ifile.readObject();
                System.out.println("Record #" + ++recnum + "  " + s);
            } catch (EOFException e1) {
                break;
            } catch (Exception e2) {
                System.err.println("Error reading from file.");
                e2.printStackTrace();
                System.exit(6);
            }
        }
    }
}