WorkerThread.java

package com.taskscheduler;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A worker thread that continuously polls the task queue and executes tasks.
 * Supports graceful shutdown via an interrupt signal.
 */
public class WorkerThread extends Thread {

    private static final AtomicInteger WORKER_COUNTER = new AtomicInteger(0);

    private final TaskQueue taskQueue;
    private final ThreadPoolStats stats;
    private volatile boolean running = true;
    private int tasksCompleted = 0;

    public WorkerThread(TaskQueue taskQueue, ThreadPoolStats stats) {
        super("Worker-" + WORKER_COUNTER.incrementAndGet());
        this.taskQueue = taskQueue;
        this.stats = stats;
        setDaemon(false);
    }

    @Override
    public void run() {
        System.out.printf("[%s] Started%n", getName());

        while (running || !taskQueue.isEmpty()) {
            try {
                // Wait up to 500ms for a task before checking running flag
                Task task = taskQueue.poll(500, TimeUnit.MILLISECONDS);

                if (task != null) {
                    executeTask(task);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                break;
            }
        }

        System.out.printf("[%s] Shutting down. Completed %d tasks.%n", getName(), tasksCompleted);
    }

    private void executeTask(Task task) {
        long waitTime = System.currentTimeMillis() - task.getSubmittedAt();
        System.out.printf("[%s] Executing %s (waited %dms)%n", getName(), task, waitTime);

        long startTime = System.currentTimeMillis();
        try {
            task.execute();
            long duration = System.currentTimeMillis() - startTime;
            tasksCompleted++;
            stats.recordCompletion(waitTime, duration);
            System.out.printf("[%s] Finished %s in %dms%n", getName(), task, duration);
        } catch (Exception e) {
            stats.recordFailure();
            System.err.printf("[%s] Task %s failed: %s%n", getName(), task, e.getMessage());
        }
    }

    public void shutdown() {
        running = false;
    }

    public int getTasksCompleted() {
        return tasksCompleted;
    }
}