How to Ensure the Main Thread Waits for Completion of Multiple Threaded Processes?

Waiting for Completion of Multiple Threaded Processes

In this code snippet, you have multiple threads created, each running a task within its own thread of execution. To ensure that the main thread waits for all the sub-threads to complete their execution before proceeding, you can implement the following approach:

1. Store Threads in an Array: Create an array to store all the created threads. This ensures organized tracking of their completion status.
2. Start All Threads: Loop through the threads array and start each thread using the start() method.
3. Join Threads in a Loop: After starting all the threads, add a loop to join each thread in the array. The join() method blocks the calling thread (in this case, the main thread) until the target thread completes its execution.

<code class="java">// ... (code as before)

public class DoSomethingInAThread implements Runnable {

    public static void main(String[] args) {
        Thread[] threads = new Thread[1000];  // Assume 1000 threads for example
        
        // Start all threads
        for (int n = 0; n < 1000; n++) {
            threads[n] = new Thread(new DoSomethingInAThread());
            threads[n].start();
        }
        
        // Wait for all threads to complete
        for (int i = 0; i < threads.length; i++) {
            threads[i].join();
        }
    }

    public void run() {
        // ... (code as before)
    }
}</code>

By using the join() method, the main thread blocks until all sub-threads have completed their execution, ensuring that your program waits for all tasks to finish before proceeding with the code that follows the loop. This approach gives you control and ensures that resources are released and the program terminates correctly.

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