Problem in SCThread2.java

[Gopisha18072003]

Sir, In the Interthread communication problem for one producer and multiple consumer there is a problem in the code. I have fixed the problem please review
class WhiteBoard {
boolean flag[] = new boolean[10];
String text;
int numberOfStudents = 0;
int count = 0;

public WhiteBoard() {
initializeFlag();
}

public void initializeFlag() {
for (int i = 0; i < 10; i++) {
flag[i] = false;
}
}

synchronized public void changeFlag(Student s) {
String name = s.name;
int idx = Integer.parseInt(name.substring(0, 1)) - 1; // Adjust index
flag[idx] = true;
}

synchronized public boolean checkFlag(Student s) {
String name = s.name;
int idx = Integer.parseInt(name.substring(0, 1)) - 1; // Adjust index
return flag[idx];
}

public void attendance() {
numberOfStudents++;
}

synchronized public void write(String t) {
System.out.println("Teacher is Writing " + t);
while (count != 0)
try {
wait();
} catch (Exception e) {
}
text = t;
initializeFlag();
count = numberOfStudents;
notifyAll();

}

synchronized public String read() {
while (count == 0)
try {
wait();
} catch (Exception e) {
}

String t = text;
count--;
if (count == 0) {
  
  notify();
}
return t;

}

}

class Teacher extends Thread {
WhiteBoard wb;

String notes[] = { "Java is language", "It is OOPs", "It is Platform Independent", "It supports Thread", "end" };

public Teacher(WhiteBoard w) {
wb = w;
}

public void run() {
for (int i = 0; i < notes.length; i++)
wb.write(notes[i]);
}

}

class Student extends Thread {
String name;
WhiteBoard wb;

public Student(String n, WhiteBoard w) {
name = n;
wb = w;
}

public void run() {
String text = "";
wb.attendance();

do {
  if (!wb.checkFlag(this)) {
    text = wb.read();
    wb.changeFlag(this);
    System.out.println(name + " Reading " + text);
    System.out.flush();

  }

} while (!text.equals("end"));

}

}

public class Main {
public static void main(String[] args) {
WhiteBoard wb = new WhiteBoard();
Teacher t = new Teacher(wb);

Student s1 = new Student("1. John", wb);
Student s2 = new Student("2. Ajay", wb);
Student s3 = new Student("3. Kloob", wb);
Student s4 = new Student("4. Smith", wb);

t.start();

s1.start();
s2.start();
s3.start();
s4.start();

}
}

[igagankapoor]

code below is improved version

class WhiteBoard {
    // ... (rest of the class remains the same)

    synchronized public String read(Student s) {
        while (count == 0) {
            try {
                wait();
            } catch (Exception e) {
            }
        }
        String t = text;
        count--;
        if (count == 0) {
            notify();
        }

        // Set the flag for this student after reading
        String name = s.name;
        int idx = Integer.parseInt(name.substring(0, 1));
        flag[idx] = true;

        return t;
    }
}

class Student extends Thread {
    // ... (rest of the class remains the same)

    public void run() {
        String text;

        wb.attendance();

        do {
            text = wb.read(this); // Pass the student object
            System.out.println(name + " Reading " + text);
            System.out.flush();
        } while (!text.equals("end"));
    }
}