Question

Primary Concepts: Priority Queues and Polymorphism

Primary Concepts

Priority Queues

Object-Oriented Frameworks

Inheritance and Polymorphism

Please read this Specification Document

Corresponding Discussion Forum

Important Design Requirement

Your design must be based on Modularity and Separation of Concerns.

Remember that interfaces represent behavior, while classes represent implementation.

The Priority Queue Data Structure and the Simulation Framework implementations must be based on "Information Hiding" and "Encapsulation".

The Software Gurus Bar is a client of the Simulation Framework.

The Simulation Framework is a client of the Priority Queue.

The Priority Queue neither knows about the Simulation Framework nor about the Software Gurus Bar.

The Simulation Framework knows about the Priority Queue (through its API), but it doesn't know about the Software Gurus Bar.

The Software Gurus Bar Application knows about the Simulation Framework through its Interface (API), but it doesn't know about the Priority Queue.

Page/Slide 11 of the above Specification Document gives a partial perspective about the Design.

The code should be written in JAVA

Answer 1

package DS;

import java.util.*;

public class PriorityQueueDriver

{

public static void main(String[] pyari)

{

Scanner in = new Scanner(System.in);

// Creating Priority queue parameterized constructor

// with initial capacity is 8 and a StudentComparator

// instance as its parameters

PriorityQueue<MyStudent> pq = new

PriorityQueue<MyStudent>

(8, new MyStudentComparator());

  

// Creates a Student object using

// parameterized constructor

// and adds the student object to priority queue  

pq.add(new MyStudent("Pyari", 99.98));

pq.add(new MyStudent("Sasmita", 87.62));

pq.add(new MyStudent("Ram", 66.22));

pq.add(new MyStudent("Manvi", 94.36));

pq.add(new MyStudent("Tnvi", 84.36));

  

// Printing names of students in priority order,poll()

// method is used to access the head element of queue

System.out.println("Students served in their " +

"priority order of total mark.");

  

// Loops till queue is not empty

while (!pq.isEmpty())

System.out.println(pq.poll().getName());

}// End of main method

}// End of driver class PriorityQueueDriver

// Defines a class MyStudentComparator implementing

// Comparator interface

class MyStudentComparator implements Comparator<MyStudent>

{

// Overriding compare() method of Comparator  

// for descending order of total

public int compare(MyStudent firstStu, MyStudent secondStu)

{

// Checks if first student total mark is less than

// second student total mark then return 1

if (firstStu.getTotal() < secondStu.getTotal())

return 1;

// Otherwise checks if first student total mark

// is greater than second student total mark

// then return -1

else if (firstStu.getTotal() > secondStu.getTotal())

return -1;

// Otherwise both are equal return 0

return 0;

}// End of method

} // End of class MyStudentComparator

// Defines a class student to store student information

class MyStudent

{

// To stores name and total mark

private String name;

private double total;

  

// Parameterized student constructor to assign

// parameter values to instance variables

public MyStudent(String na, double tot)

{

name = na;

total = tot;

}// End of parameterized constructor

// Method to return name

public String getName()

{

return name;

}// End of method

  

// Method to return total

public double getTotal()

{

return total;

}// End of method

}// End of class Student

Sample Output:

Students served in their priority order of total mark.
Pyari
Manvi
Sasmita
Tnvi
Ram