CountDownLatch example

Suppose we have a server-side core Java application that uses a services architecture,

where multiple services are provided by multiple threads.

The application cannot start processing until all services have started successfully.

In this scenario, we can use CountDownLatch to ensure that the main thread waits until

all services have started before proceeding with further processing

public class CountDownLatchExample {
private static final int NUM_SERVICES = 3;
private static final CountDownLatch latch = new CountDownLatch(NUM_SERVICES);

public static void main(String[] args) {
// Start the services in separate threads
for (int i = 0; i < NUM_SERVICES; i++) {
Thread serviceThread = new Thread(new Service());
serviceThread.start();
        }

try {
// Wait for all services to start
System.out.println("Waiting for " + latch.getCount() +  " services to start");
latch.await();
System.out.println("All services have started. Proceeding with further processing...");
        } catch (InterruptedException e) {
e.printStackTrace();
        }
    }

static class Service implements Runnable {
@Override
public void run() {
// Simulate some processing
try {
Thread.sleep(2000);
System.out.println("Started ");
            } catch (InterruptedException e) {
e.printStackTrace();
            }

// Service has started, decrement the latch count
latch.countDown();
        }
    }
}

Waiting for 3 services to start

Started

Started

Started

All services have started. Proceeding with further processing...