Java OCA OCP Practice Question 2502

Question

Examine the following code and select the correct options. 

public class Main {
    public static void main(String[] args) {
        Thread bug = new Thread() {
            public void run() {
                System.out.print("check bugs");
            }/*w w  w .  j a  va2 s.  c o  m*/
        };
        Thread t = new Thread(bug);
        t.run();
    }
}
  • a No code output
  • b Code prints check bugs once.
  • c Code prints check bugs twice.
  • d Code prints check bugs in an infinite loop.
  • e Replacing t.run() with t.start() will throw a compilation exception.
  • f Replacing t.run() with t.start() will generate the same output on the system's console.


b, f

Note

The following code creates an anonymous class that subclasses class Thread.

Its instance is referred by bug, a reference variable of type Thread. 

Thread bug = new Thread() {
    public void run() {
        System.out.print("check bugs");
    }
 };

Because class Thread implements the Runnable interface, you can pass its instance as a target object to instantiate another Thread instance, t:. 

Thread t = new Thread(bug);

The variable t refers to an anonymous class instance that overrides its method run().

So calling t.run() executes the overridden method run() and prints check bugs only once.

Option (f) is correct.

Even though calling t.run() doesn't start a separate thread of execution and t.start() does, both will print check bugs once on the system's console.




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