public class Task240725 {
    private static synchronized void print(String msg) {
        System.out.print(msg + " ");
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(() -> print("Hello"));
        Thread t2 = new Thread(() -> print("World"));
        
        t1.start();
        t2.run();
        
        try {
            t1.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

import java.util.concurrent.locks.ReentrantLock;

public class Task250725 {
    public static void main(String[] args) {
        ReentrantLock lock = new ReentrantLock();
        try {
            lock.lock();
            System.out.println("First lock");
            lock.lock();
            System.out.println("Second lock");
        } finally {
            lock.unlock();
        }
    }
}