Try It Yourself - SyntaxStudy Editor

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import java.util.concurrent.atomic.AtomicInteger;

public class ThreadDemo {

// Runnable task (preferred over extending Thread)
    static class CounterTask implements Runnable {
        private final String name;
        private final int    count;

CounterTask(String name, int count) {
            this.name  = name;
            this.count = count;
        }

@Override
        public void run() {
            for (int i = 1; i <= count; i++) {
                System.out.printf("[%s] step %d%n", name, i);
                try {
                    Thread.sleep(50); // simulate work
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt(); // restore flag
                    System.out.println(name + " interrupted");
                    return;
                }
            }
        }
    }

// Thread-safe counter using AtomicInteger
    static AtomicInteger sharedCounter = new AtomicInteger(0);

public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(new CounterTask("Alpha", 3));
        Thread t2 = new Thread(new CounterTask("Beta",  3));

t1.start();
        t2.start();

t1.join(); // wait for t1 to finish
        t2.join(); // wait for t2 to finish

System.out.println("Both threads finished");

// Concurrent increments with AtomicInteger
        Runnable incrementer = () -> {
            for (int i = 0; i < 1000; i++) sharedCounter.incrementAndGet();
        };
        Thread[] workers = new Thread[5];
        for (int i = 0; i < 5; i++) { workers[i] = new Thread(incrementer); workers[i].start(); }
        for (Thread w : workers) w.join();
        System.out.println("Shared counter (expected 5000): " + sharedCounter.get());
    }
}