You have been hired by the CS Department to write code to help synchronize a pro

Question

You have been hired by the CS Department to write code to help synchronize a professor and his/her students during office hours. The professor, of course, wants to take a nap if no students are around to ask questions; if there are students who want to ask questions, they must synchronize with each other and with the professor so that
- only one person is speaking at any one time,
- each student question is answered by the professor, and
- no student asks another question before the professor is done answering the previous one.
You are to write four procedures: AnswerStart(), AnswerDone(), QuestionStart() and QuestionDone().
The professor loops running the code: AnswerStart(); give answer; AnswerDone(). AnswerStart doesn’t return until a question has been asked. Each student loops running the code: QuestionStart(); ask question; QuestionDone(). QuestionStart() does not return until it is the student’s turn to ask a question. Since professors consider it rude for a student not to wait for an answer, QuestionEnd() should not return until the professor has finished answering the question. You can use a command line interface for this program. You are free to make other design choices and be creative in your implementation. You may use any programming language of your choice.

Explanation / Answer

//ok, here is some rough code that gives the desired output and uses synchronization.

//compile it and run.

 

public class Demo
{
    public static void main(String[]args)
    {
        System.out.println("Welcome to the lecture !!! ");
       
        Classroom c = new Classroom();
        Professor p = new Professor();
        c.setProf(p);
        p.setClass(c);
       
        Student s1 = new Student("S1", "germany",c);
        Student s2 = new Student("S2", "england",c);
        Student s3 = new Student("S3", "USA",c);
        Student s4 = new Student("S4", "India",c);
        Student s5 = new Student("S5", "China",c);
        s1.start();
        s2.start();
        s3.start();
        s4.start();
        s5.start();
   
    }


}

class Classroom
{
    Professor prof;
   
    public void setProf(Professor p)
    {
        prof = p;
    }
   
    public synchronized void currentStudent(String msg, String name)
    {
        System.out.println(name + " says : " + msg);
        prof.answer(name);
        System.out.println(" ");
    }
   
}

class Student extends Thread
{
    String name;
    String ques;
    Classroom cl;
   
    Student(String n, String q, Classroom c)
    {
        name = n;
        ques = q;
        cl = c;
    }
   
    public void run()
    {
        String message = "Sir where is " +  ques + " ? ";
       
        for(int i = 0; i < 3; i++) // ask the same question 3 times !
        {
            cl.currentStudent(message, name);
            //ask a question and wait or sleep before you ask again.
           
            try
            {
                Thread.sleep(1500); // sleep for 1.5 sec.
            }catch(Exception ex){System.out.println("error : " + ex);}
           
        }
       
    }//run
   
   
}

class Professor
{
    String pro = "Nutty Prof";
    Classroom cl;
    String ans = "I dont know !";
   
    public void setClass(Classroom c)
    {
        cl = c;
    }

    public void answer(String name)
    {
        System.out.println("PROF says : Dear " + name + " " + ans);
    }
   
}

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