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 each student question is answered by the professor, and time, no student asks another question before the professor is done answering the previous one. You are to write four procedures: AnswerStartO, AnswerDone), QuestionStart) and QuestionDane) 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, QuestionEndhould not return until the professor has finished answering the question. You can command line interface for this program. You are free to make use a other design choices and be creative in your implementation. You may use any programming language of your choice.

Answer 1

//compile it and run.

public class Demo
{
public static void main(String[]args)
{
System.out.println("Welcome to the lecture !!!\n");

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("\n");
}

}

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);
}

}