Given: class Worker extends Thread { CyclicBarrier cb; public Worker (CyclicBarrier cb) { this.cb = cb; } public void run () { try { cb.await(); System.out.println ("Worker..."); } catch (Exception…

Question

Options

• AAt line n2, insert CyclicBarrier cb = new CyclicBarrier(2, master);
• BReplace line n1 with class Master extends Thread { }
• CAt line n2, insert CyclicBarrier cb = new CyclicBarrier(1, master);
• DAt line n2, insert CyclicBarrier cb = new CyclicBarrier(master);

• A
  13% (6)
• B
  4% (2)
• C
  76% (34)
• D
  7% (3)

Explanation

Option C works because CyclicBarrier(1, master) creates a barrier that trips as soon as 1 thread calls await(). When the single Worker thread calls cb.await(), the barrier immediately fires, executing master.run() (printing "Master..."), then releases the Worker to continue and print "Worker...". Both run() methods execute exactly as required.

Why the distractors fail:

• A (new CyclicBarrier(2, master)) requires 2 threads to call await() before the barrier trips, but only one Worker is started - it blocks forever and neither print statement executes.
• B (changing Master to extends Thread) is irrelevant; master is never .start()ed anywhere in the code fragment, so its run() still never executes.
• D (new CyclicBarrier(master)) is a compilation error - there is no CyclicBarrier constructor that accepts only a Runnable; valid constructors require an int parties argument.

Memory tip: Match the party count to the number of threads that actually call await(). Count the .start() calls in scope - here there is exactly one (worker.start()), so parties = 1. The Runnable second argument is a bonus action that fires at the barrier, giving you a clean way to run non-thread Runnables without extending Thread.

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