Question

Create a Java application that meets the following specifications. Write whatever public and private methods are necessary. Put all of these classes in a package called persistence1.

• Student has a String name, a double GPA, and a reasonable equals() method.
• Course has a String name, an ArrayList of Students, and a reasonable equals() method. It will also need a method to add a Student.
• StudentPersister uses binary file I/O to save and retrieve Students and Lists of Students. CoursePersister does the same for Courses and Lists of Courses. The save methods will need to deal with NotSerializableExceptions. Make sure that the read methods do not cause crashes if you attempt to read files that do not contain the anticipated objects.

Answer 1

// Please write each class in a separate file :

// Class 1 : Student.java

package persistence1;

import java.io.Serializable;

public class Student implements Serializable{

/**

*

*/

private static final long serialVersionUID = -6123469366535229726L;

private String name;

private double gpa;

  

  

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public double getGpa() {

return gpa;

}

public void setGpa(double gpa) {

this.gpa = gpa;

}

  

public Student() {

  

}

  

public Student(String name, double gpa) {

super();

this.name = name;

this.gpa = gpa;

}

  

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

long temp;

temp = Double.doubleToLongBits(gpa);

result = prime * result + (int) (temp ^ (temp >>> 32));

result = prime * result + ((name == null) ? 0 : name.hashCode());

return result;

}

  

@Override

public boolean equals(Object obj) {

if (this == obj)

return true;

if (obj == null)

return false;

if (getClass() != obj.getClass())

return false;

Student other = (Student) obj;

if (Double.doubleToLongBits(gpa) != Double.doubleToLongBits(other.gpa))

return false;

if (name == null) {

if (other.name != null)

return false;

} else if (!name.equals(other.name))

return false;

return true;

}

@Override

public String toString() {

return "Student [name=" + name + ", gpa=" + gpa + "]";

}

  

}

// Class 2: Course.Java

package persistence1;

import java.io.Serializable;

import java.util.ArrayList;

public class Course implements Serializable{

  

/**

*

*/

private static final long serialVersionUID = -4616187168507101589L;

private String name;

private ArrayList<Student> arrStdList = new ArrayList<>();

  

  

public Course() {

super();

}

  

public Course(String name, ArrayList<Student> arrStdList) {

super();

this.name = name;

this.arrStdList = arrStdList;

}

  

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public ArrayList<Student> getStdList() {

return arrStdList;

}

public void setStdList(ArrayList<Student> arrStdList) {

this.arrStdList = arrStdList;

}

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

result = prime * result + ((name == null) ? 0 : name.hashCode());

result = prime * result + ((arrStdList == null) ? 0 : arrStdList.hashCode());

return result;

}

@Override

public boolean equals(Object obj) {

if (this == obj)

return true;

if (obj == null)

return false;

if (getClass() != obj.getClass())

return false;

Course other = (Course) obj;

if (name == null) {

if (other.name != null)

return false;

} else if (!name.equals(other.name))

return false;

if (arrStdList == null) {

if (other.arrStdList != null)

return false;

} else if (!arrStdList.equals(other.arrStdList))

return false;

return true;

}

  

public void addStudent(Student s)

{

arrStdList.add(s);

}

@Override

public String toString() {

return "Course [name=" + name + ", arrStdList=" + arrStdList + "]";

}

}

// Class 3 : StudentPersister.java

package persistence1;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.util.ArrayList;

public class StudentPersister {

  

  

static void save(ArrayList<Student> s)

{

try {

FileOutputStream f = new FileOutputStream(new File("Student.txt"));

ObjectOutputStream o = new ObjectOutputStream(f);

// Write objects to file

o.writeObject(s);   

o.close();

f.close();

} catch (FileNotFoundException e) {

System.out.println("File not found");

} catch (IOException e) {

System.out.println("Error initializing stream");

}

}

  

static ArrayList<Student> read(String loc)

{

ArrayList<Student> s1 = null;

try

{

  

FileInputStream fi = new FileInputStream(new File(loc));

ObjectInputStream oi = new ObjectInputStream(fi);

// Read objects

s1 = (ArrayList<Student>) oi.readObject();

oi.close();

fi.close();

} catch (FileNotFoundException e) {

System.out.println("File not found");

} catch (IOException e) {

System.out.println("Error initializing stream");

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

  

return s1;

}

  

}

// Class 4. CoursePersister.java

package persistence1;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.util.ArrayList;

public class CoursePersister {

static void save(ArrayList<Course> s)

{

try {

FileOutputStream f = new FileOutputStream(new File("Course.txt"));

ObjectOutputStream o = new ObjectOutputStream(f);

// Write objects to file

o.writeObject(s);   

o.close();

f.close();

} catch (FileNotFoundException e) {

System.out.println("File not found");

} catch (IOException e) {

System.out.println("Error initializing stream");

}

}

  

static ArrayList<Course> read(String loc)

{

ArrayList<Course> c1 = null;

try

{

  

FileInputStream fi = new FileInputStream(new File(loc));

ObjectInputStream oi = new ObjectInputStream(fi);

// Read objects

c1 = (ArrayList<Course>) oi.readObject();

oi.close();

fi.close();

} catch (FileNotFoundException e) {

System.out.println("File not found");

} catch (IOException e) {

System.out.println("Error initializing stream");

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

  

return c1;

}

}

// Class 5 : Junit Student class : StudentPersisterTest.java

package persistence1;

import static org.junit.Assert.*;

import java.util.ArrayList;

import org.junit.BeforeClass;

import org.junit.Test;

public class StudentPersisterTest {

@BeforeClass

public static void setUpBeforeClass() throws Exception {

  

//StudentPersister sp = new StudentPersister();

}

  

@Test

public void test() {

Student s = new Student("Sourabh",8.2);

Student s2 = new Student("Raja",7.9);

String loc="Student.txt";

ArrayList<Student> sList = new ArrayList<>();

sList.add(s);

sList.add(s2);

StudentPersister.save(sList);

ArrayList<Student> sList2 = StudentPersister.read(loc);

System.out.println(sList2);

  

fail("Not yet implemented");

}

}

// Class 6 : junit class for Course ; CoursePersisterTest.java

package persistence1;

import static org.junit.Assert.*;

import java.util.ArrayList;

import org.junit.BeforeClass;

import org.junit.Test;

public class CoursePersisterTest {

@BeforeClass

public static void setUpBeforeClass() throws Exception {

}

@Test

public void test() {

  

Student s1 = new Student("Sourabh",8.2);

Student s2 = new Student("Raja",7.9);

String loc="Course.txt";

Course c = new Course();

c.addStudent(s1);

c.addStudent(s2);

c.setName("maths");

  

Course c2 = new Course();

c2.addStudent(s1);

c2.addStudent(s2);

c2.setName("computer");

  

ArrayList<Course> cList = new ArrayList<>();

cList.add(c);

cList.add(c2);

CoursePersister.save(cList);

ArrayList<Course> cList2 = CoursePersister.read(loc);

System.out.println(cList2);

  

  

fail("Not yet implemented");

}

}

// Here we have implemented Serializable interface in both classes, so need to worry about NotSerializableExceptions.

// Out put :

/*

Output 1.

[Student [name=Sourabh, gpa=8.2], Student [name=Raja, gpa=7.9]]

Output 2.

[Course [name=maths, arrStdList=[Student [name=Sourabh, gpa=8.2], Student [name=Raja, gpa=7.9]]], Course [name=computer, arrStdList=[Student [name=Sourabh, gpa=8.2], Student [name=Raja, gpa=7.9]]]]

*/