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.

• The student has a String name, a double GPA, and a reasonable equals() method.
• The 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 the 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.
• Write a JUnit test case for each of the Persisters. Test to make sure StudentPersister correctly saves and retrieves Students and lists of Students, and that CoursePersister correctly saves and retrieves Courses and lists of Courses.

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]]]]
*/