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## Quiz on Chapter 12

This page contains questions on Chapter 12 of Introduction to Programming Using Java. You should be able to answer these questions after studying that chapter. Sample answers to these questions can be found here.

Question 1:

Write a complete subclass of Thread to represent a thread that writes out the numbers from 1 to 10. Then write some code that creates and starts a thread belonging to that class.

Question 2:

Suppose that thrd is an object of type Thread. Explain the difference between calling thrd.start() and calling thrd.run().

Question 3:

What is a race condition?

Question 4:

How does synchronization prevent race conditions, and what does it mean to say that synchronization only provides mutual exclusion?

Question 5:

Suppose that a program uses a single thread that takes 4 seconds to run. Now suppose that the program creates two threads and divides the same work between the two threads. What can be said about the expected execution time of the program that uses two threads?

Question 6:

What is an ArrayBlockingQueue and how does it solve the producer/consumer problem?

Question 7:

What is a thread pool?

Question 8:

Network server programs are often multithreaded. Explain what this means and why it is true.

Question 9:

Why does a multithreaded network server program often use many times more threads than the number of available processors?

Question 10:

Consider the ThreadSafeCounter example from Subsection 12.1.3:

    public class ThreadSafeCounter {

       private int count = 0;  // The value of the counter.

       synchronized public void increment() {
          count = count + 1;
       }

       synchronized public int getValue() {
          return count;
       }

    }

The increment() method is synchronized so that the caller of the method can complete the three steps of the operation "Get value of count," "Add 1 to value," "Store new value in count" without being interrupted by another thread. But getValue() consists of a single, simple step. Why is getValue() synchronized? (This is a deep and tricky question.)

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