3.java

class SyncThread implements Runnable {

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "_Sync: " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
        synchronized (this) {
            try {
                System.out.println(Thread.currentThread().getName() + "_Sync_Start: " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
                Thread.sleep(2000);
                System.out.println(Thread.currentThread().getName() + "_Sync_End: " + new SimpleDateFormat("HH:mm:ss").format(new Date()));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
F_thread1_Sync: 23:23:56
F_thread2_Sync: 23:23:56
F_thread3_Sync: 23:23:56
F_thread1_Sync_Start: 23:23:56
F_thread4_Sync: 23:23:56
F_thread2_Sync_Start: 23:23:56
F_thread3_Sync_Start: 23:23:56
F_thread1_Sync_End: 23:23:58
F_thread2_Sync_End: 23:23:58
F_thread3_Sync_End: 23:23:58
F_thread4_Sync_Start: 23:23:58
F_thread4_Sync_End: 23:24:00