Thread signaling refers to a mechanism where one thread communicates with another thread to indicate that a certain condition or event has occurred. This can be achieved using various synchronization techniques such as wait-notify, condition variables, semaphores, or specialized thread-safe classes.
Program
This program illustrates thread signaling with an example involving a Teacher thread and a Student thread. Assume we have a scenario where the Teacher thread needs to signal the Student thread to start a quiz after preparing the questions.
//ThreadSignalingDemo.java
class Classroom {
// Flag to indicate whether the quiz is ready
private boolean quizReady = false;
public synchronized void prepareQuiz() {
// Teacher prepares the quiz questions
System.out.println("Teacher is preparing the quiz...");
// Simulate some delay in preparing the quiz
try {
Thread.sleep(2000); // 2 seconds
} catch (InterruptedException e) {
e.printStackTrace();
}
// Quiz is ready
quizReady = true;
// Notify all waiting students that quiz is ready
notifyAll();
}
public synchronized void takeQuiz() {
// Student waits until quiz is ready
while (!quizReady) {
try {
wait(); // Wait until notified by the Teacher
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// Start taking the quiz
System.out.println("Student is taking the quiz...");
}
}
public class ThreadSignalingDemo {
public static void main(String[] args) {
Classroom classroom = new Classroom();
// Create Teacher thread
Thread teacherThread = new Thread(() -> {
classroom.prepareQuiz();
});
// Create Student thread
Thread studentThread = new Thread(() -> {
classroom.takeQuiz();
});
// Start both threads
teacherThread.start();
studentThread.start();
}
}
/*
C:>javac ThreadSignalingDemo.java
C:>java ThreadSignalingDemo
Teacher is preparing the quiz...
Student is taking the quiz...
*/