Final Quiz

class MyThread extends Thread {

public void run() {

System.out.println("Child Thread");

}

public static void main(String[] args) {

MyThread t = new MyThread();

t.start();

System.out.println("Main Thread");

}

}

• Only "Child Thread"
  

• Only "Main Thread"
  

• "Main Thread" followed by "Child Thread"
  

• Either "Child Thread" or "Main Thread" may come first

What will be the output if run() is called instead of start()?

MyThread t = new MyThread();

t.run();

System.out.println("Main Thread");

• "Child Thread" and "Main Thread" printed from different threads
  

• "Child Thread" and "Main Thread" printed from the same thread
  

• Only "Main Thread"
  

• Compilation error

What is the state of a thread once the start() method is called but before run() is executed?

• New
  

• Runnable
  

• Running
  

• Blocked

public class Test extends Thread {

public void run() {

System.out.println("Running");

}

public static void main(String[] args) {

Test t1 = new Test();

Test t2 = new Test();

t1.start();

t2.start();

}

}

How many threads are running?

• 1
  

• 2
  

• 3
  

• 4

public class SyncTest {

public synchronized void test() {

System.out.println(Thread.currentThread().getName() + " is running");

}

public static void main(String[] args) {

SyncTest obj = new SyncTest();

Thread t1 = new Thread(() -> obj.test());

Thread t2 = new Thread(() -> obj.test());

t1.start();

t2.start();

}

}

• Both threads run together
  
  

• Only one thread runs
  
  

• Threads run one after another due to synchronization
  
  

• Compilation error

public class MyClass {

public synchronized void methodA() {

System.out.println("Method A - " + Thread.currentThread().getName());

}

public void methodB() {

synchronized (this) {

System.out.println("Method B - " + Thread.currentThread().getName());

}

}

}

If two threads call methodA() and methodB() on the same object, which statement is true?

• Both can execute simultaneously
  

• Only one can execute at a time
  

• They may deadlock
  

• It causes a compilation error

public class Counter {

private int count = 0;

public synchronized void increment() {

count++;

}

public int getCount() {

return count;

}

}

Two threads each call increment() 1000 times. What can be said about getCount()?

• 
  Will cause an exception

• B. Always less than 2000
  

• Could be 2000 or less
  

• Always 2000

Which statement is true about the difference between synchronized method and synchronized(this) block?

• synchronized method is faster
  

• Both lock different monitors
  

• Both lock the same object monitor (this)
  

• synchronized(this) cannot be used in constructors

What does a static synchronized method lock on?

• The instance of the class
  

• 
  The .class object (i.e., class-level monitor)

• 
  The thread that calls it

• Nothing, it behaves like a non-synchronized method

class Example {

public static synchronized void staticMethod() {

System.out.println("Static method");

}

public synchronized void instanceMethod() {

System.out.println("Instance method");

}

}

• Yes
  

• No
  

• Only if both methods are synchronized
  

• Only on different objects