Question

ist all possible results b. tions and options for controlig till 44. What is the output of each of the following code sequences? List all pe and explain your answers. a. Counter c = new Counter(); c.increment(); c.increment(); System.out.println(c); Counter c = new Counter(); Runnable r = new Increase (c. 3): Thread t = new Thread (r); t.start(): System.out.println(c): c. Counter c = new Counter(); Runnable r = new Increase (c, 3): Thread t = new Thread (r); c.increment(): t.start(); System.out.println(c):

Answer 1

a.  Answer: 2

Explanation:

Counter c = new Counter();   // create an object of Counter class with default constructor that sets the counter to zero
       c.increment(); c.increment(); // two times call the increment() method, now final value of counter is 2.
       System.out.println(c); // toString() method is called while print the object and it should print 2.

b. Answer: 0

Explanation:

Counter c = new Counter(); // create an object of Counter class with default constructor that sets the counter to zero
       Runnable r = new Increase(c, 3); // reference r of Runnable interface refers to the object of Increase class. In the constructor of Increase class accepts two arguments: Counter class reference c and a integer value
       Thread t = new Thread(r); // create an object of Thread class that refers to the object of Increase class
       t.start(); // start() method is called, and hence run() method invoked automatically
       System.out.println(c); // toString() method is called while print the object and but it may print 0, since main() thread may ends before thread t. Note that sometimes it may print 3 also.

c. Answer: 1

Explanation:

Counter c = new Counter();
       Runnable r = new Increase(c, 3);
       Thread t = new Thread(r);
       c.increment(); t.start();   // The the increment() method is called once. Then start() method is called, and hence run() method invoked automatically. In the run() method the value of count increase by 3.
       System.out.println(c);  // toString() method is called while print the object and but it may print 1, since main() thread may ends before thread t. Note that sometimes it may print 4 also.

d. Answer 1

Explanation:

Counter c = new Counter();
       Runnable r = new Increase(c, 3);
       Thread t = new Thread(r);
       t.start(); c.increment();  // start() method is called, and hence run() method invoked automatically. Then the increment() method is called once.
       System.out.println(c);  // toString() method is called while print the object and but it may print 1, since main() thread may ends before thread t. Note that sometimes it may print 4 also.

e. Annwer 4

Explanation:

Counter c = new Counter();
       Runnable r = new Increase(c, 3);
       Thread t = new Thread(r);
       t.start(); t.join(); //here join method is called to ensure that thread t ends before of main thread
       c.increment();
       System.out.println(c);  // toString() method is called while print the object and it print 4, since t thread ends before main thread.

f. Answer 4

Explanation:

Counter c = new Counter();
       Runnable r = new Increase(c, 3);
       Thread t = new Thread(r);
       t.start(); c.increment();
       t.join();  //here join method is called (after the calling of increment method) to ensure that thread t ends before of main thread
       System.out.println(c);  // toString() method is called while print the object and it print 4, since t thread ends before main thread.