멀티스레딩

import java.util.concurrent.*;

public class MultithreadingExample {
    public static void main(String[] args) throws Exception {
        // 1. Thread 클래스 상속
        Thread thread1 = new Thread(() -> {
            System.out.println("스레드 1: " + Thread.currentThread().getName());
        });
        thread1.start();

        // 2. ExecutorService 사용 (권장)
        ExecutorService executor = Executors.newFixedThreadPool(4);

        for (int i = 0; i < 10; i++) {
            final int taskId = i;
            executor.submit(() -> {
                System.out.println("Task " + taskId + " 실행: " +
                    Thread.currentThread().getName());
            });
        }

        executor.shutdown();
        executor.awaitTermination(1, TimeUnit.MINUTES);

        // 3. 동기화가 필요한 경우
        Counter counter = new Counter();
        Thread t1 = new Thread(() -> { for(int i=0; i<1000; i++) counter.increment(); });
        Thread t2 = new Thread(() -> { for(int i=0; i<1000; i++) counter.increment(); });
        t1.start(); t2.start();
        t1.join(); t2.join();
        System.out.println("카운터: " + counter.getCount()); // 2000
    }
}

class Counter {
    private int count = 0;
    public synchronized void increment() { count++; }
    public int getCount() { return count; }
}