java lock and unlock a example

public class PrintQueue {
    private final Lock queueLock = new ReentrantLock();

    public void printJob(Object document){
        queueLock.lock();
        try{
            Long duration = (long)(Math.random() * 10000);
            System.out.println(Thread.currentThread().getName() + ": PrintQueue: Printing a Job during " + (duration/1000) + " seconds");
            Thread.sleep(duration);
        }catch(InterruptedException e){
            e.printStackTrace();
        }finally{
            queueLock.unlock();
        }
    }
}

public class Job implements Runnable {
    private PrintQueue printQueue;

    public Job(PrintQueue printQueue){
        this.printQueue = printQueue;
    }

    @Override
    public void run(){
        System.out.printf("%s: Going to print a document\n", Thread.currentThread().getName());
        printQueue.printJob(new Object());
        System.out.printf("%s: The document had been printed\n", Thread.currentThread().getName());
    }
}

public class Main {
    public static void main(String[] args){
        PrintQueue printQueue= new PrintQueue();
        Thread thread[] = new Thread[10];
        for(int i=0; i<10; i++){
            thread[i] = new Thread(new Job(printQueue), "Thread" + i);
        }

        for(int i=0; i<10; i++){
            thread[i].start();
        }
    }
}