Question 1

What is likely to be true when thread one is downloading a 1MB file while thread two is downloading another 1MB file?
A) The files download twice as fast as they would if one thread downloaded both files.
B) The files download half as fast as they would if one thread downloaded both files.
C) When thread one is half done, thread two is about half done.
D) The faster thread will interrupt the other thread.

Accepted Answer

The progress of both threads is likely to be similar if they are performing the same task under similar conditions, so when one thread is halfway done, the other is likely to be around the same point. The speed of downloading depends on the network bandwidth and server response, not solely on the number of threads.

Question 2

What should be done to get the attention of a thread?
A) call the thread's stop method
B) call the thread's run method
C) call the thread's interrupt method
D) call the thread's sleep method

Accepted Answer

Calling the interrupt method on a thread will cause it to throw an InterruptedException and potentially wake up any code waiting on that thread. This can be useful for getting a thread's attention and allowing it to stop executing gracefully. Calling the stop method is deprecated and can cause unpredictable behavior. Calling the run method will just execute the thread's code synchronously rather than asynchronously. Calling the sleep method will pause the current thread, not the specified thread, for a set amount of time.

Question 3

Which of the following definitely indicates that a thread has terminated?
I The run method has completed
II The method Thread.interrupted returns true
III The run method catches an InterruptedException
A) I
B) II
C) I and II
D) II and III

Accepted Answer

The run method completing indicates that the thread has finished executing. The other options do not definitively indicate termination.

Question 4

The sleep method is terminated with a(n) __________ whenever a sleeping thread is interrupted.
A) InterruptedException
B) SleepException
C) lock
D) SignalException

Accepted Answer

When a sleeping thread is interrupted, the sleep method is terminated with an InterruptedException. This allows the thread to handle the interruption gracefully and take appropriate action.

Question 5

Which argument(s) present(s) the best case(s) for extending the Thread class rather than using the Runnable interface in conjunction with a thread pool?
I Thread sub-classes will all execute independently
II Runnable objects will waste more system resources
III Thread sub-classes can execute faster on a single CPU than Runnable objects
A) I
B) II
C) III
D) II and III

Accepted Answer

Extending the Thread class is not inherently more resource-intensive or faster than using Runnable. The main reason to extend Thread is to create a unique thread with specific behavior, not for performance or resource efficiency.

Question 6

What course of action should be followed when a thread has been interrupted?
A) the thread should terminate
B) the thread should do what a programmer thinks is appropriate
C) the thread should go to sleep
D) the thread should call the Thread.interrupted method

Accepted Answer

The appropriate action when a thread is interrupted depends on the specific requirements of the application and what the programmer deems necessary, such as cleaning up resources or stopping execution gracefully.

Question 7

Suppose thread one is downloading a 800KB file while another thread is processing the same file on a multi-CPU machine. Suppose further that one time slice allows the first thread to download about 10KB and that the second thread can process 10KB of the file in one time slice. What is the minimum number of CPUs that will allow the job to be completed in roughly half the time of a single-CPU machine?
A) 1
B) 2
C) 3
D) 4

Accepted Answer

The first thread downloads 10KB per time slice, and the second thread processes 10KB per time slice. So, on a single-CPU machine, the job will take 80 time slices to complete. On a 2-CPU machine, the job will take 40 time slices to complete, which is roughly half the time of a single-CPU machine.

Question 8

Suppose thread one is downloading a 800KB file while another thread is processing the same file on a single CPU machine. Suppose further that one time slice allows the first thread to download about 10KB and that the second thread can process 10KB of the file in one time slice. How many total time slices will it take to process half the file?
A) thirty
B) forty
C) eighty
D) hundred

Accepted Answer

To process half of the 800KB file, 400KB needs to be processed. Since each time slice allows processing of 10KB, it will take 40 time slices to process 400KB. Additionally, since the file must be downloaded first, it will take another 40 time slices to download 400KB. Therefore, the total time slices required is 40 (download) + 40 (process) = 80 time slices.

Question 9

Suppose thread one is downloading a 800KB file while another thread is processing the same file on a single CPU machine. Suppose further that one time slice allows the first thread to download about 10KB and that the second thread can process 10KB of the file in one time slice. How many total time slices will it take to see the first 10KB of the processed file?
A) one
B) two
C) eight
D) ten

Accepted Answer

The answer of Suppose thread one is downloading a 800KB...

Question 10

Which argument(s) present(s) the best case(s) for using the Runnable interface rather than extending the Thread class?
I Thread sub-classes are harder to write
II Runnable objects can be passed into thread pools
III Less time is wasted in creating and destroying thread objects
A) I
B) II
C) II and III
D) I and II

Accepted Answer

Runnable objects can be passed into thread pools, and less time is wasted in creating and destroying thread objects.

Question 11

____ occur(s) if the effect of multiple threads on shared data depends on the order in which the threads are scheduled.
A) Pooling
B) Interrupted exceptions
C) Deadlocks
D) Race conditions

Accepted Answer

A race condition occurs when multiple threads access and manipulate shared data at the same time, and the outcome of this manipulation depends on the order in which the threads are executed. This can result in unpredictable behavior and data corruption.

Question 12

Insert the statement that would start the following thread. Thread firstThread = new Thread(myRunnable);
____________________
A) firstThread.run();
B) firstThread.start();
C) run();
D) start();

Accepted Answer

When creating a new thread, we need to use the Thread constructor and pass a Runnable object to it. The next step is to start the execution of the thread by calling the start() method on the thread object created. Therefore, the correct statement to start a thread is firstThread.start();. Option A is incorrect because calling run() directly will not create a new thread, but simply execute the code on the main thread. Option C and D are also incorrect because run() and start() are instance methods and need to be called on a thread object, not directly.

Question 13

Each thread runs for a short amount of time, called a ____________________.
A) thread allotment
B) thread time slot
C) time slice
D) run time slice

Accepted Answer

The term commonly used to describe the short amount of time that a thread runs for is "time slice". Options A, B, and D are not as commonly used or specific to this context.

Question 14

In the initial release of the Java library, the Thread class had a stop method to terminate a thread. However, that method is now _______________
A) forbidden
B) not recommended
C) unwise
D) deprecated

Accepted Answer

The stop method is now deprecated, meaning it is no longer recommended for use and may be removed in future versions of Java. It is advised to use other methods such as interrupt() or a boolean flag to gracefully stop a thread.

Question 15

Suppose thread one is downloading a 800KB file while another thread is processing the same file on a single CPU machine. Suppose further that one time slice allows the first thread to download about 10KB and that the second thread can process 10KB of the file in one time slice. Approximately how does the time to complete the entire job compare to having a single thread do the work?
A) The threaded way will be twice as fast.
B) The threaded way will be twice as slow.
C) The time depends heavily on the thread scheduler.
D) The ways will take about the same time.

Accepted Answer

The answer of Suppose thread one is downloading a 800KB...

Question 16

Suppose thread one is downloading a large file while another thread is processing the same file on a single CPU machine. Suppose further that one time slice allows the first thread to download about 10KB and that the second thread can process 10KB of the file in one time slice. What is the main benefit of using two threads rather than using a single thread to do both parts of the job?
A) accuracy of the results
B) speed to compete entire job
C) speed of availability of partial results
D) less memory is used

Accepted Answer

Using two threads allows partial results to be available sooner, as downloading and processing can occur concurrently, even if the entire job isn't completed faster.

Question 17

Which of the following definitely indicates that a thread has been interrupted by another thread?
I The run method has completed
II The method Thread.interrupted returns true
III The run method catches an InterruptedException
A) I
B) II
C) I and II
D) II and III

Accepted Answer

The method Thread.interrupted returning true and catching an InterruptedException both indicate that a thread has been interrupted. The completion of the run method does not necessarily indicate an interruption.

Question 18

The ____________ occurs when a thread that is not running is interrupted.
A) InterruptException
B) InterruptedException
C) ThreadException
D) ThreadTerminatedException

Accepted Answer

A thread that is not currently running can be interrupted using the interrupt() method of the Thread class. This method throws the InterruptedException if the thread is in a waiting or sleeping state when interrupted.

Question 19

The ___________ method does not actually cause threads to terminate; it merely sets a Boolean field in the thread data structure.
A) stop
B) await
C) sleep
D) interrupt

Accepted Answer

The interrupt method sets a thread's interrupt status flag so that it can be detected and responded to appropriately by the target thread, but it does not force the target thread to stop immediately. Therefore, choice D is the best answer. Choices A, B, and C all involve actively causing a thread to stop or pause.

Question 20

A(n) ____ uses a small number of threads to execute a large number of runnables.
A) embedded system
B) condition object
C) thread pool
D) race condition

Accepted Answer

A thread pool is a group of pre-initialized threads that are available to perform a set of tasks. It manages the execution of asynchronous tasks using a small number of threads by recycling and reusing these threads to execute a large number of runnables, instead of creating a new thread for every task. This improves performance and reduces overhead.

Quiz 21: Multithreading

What is likely to be true when thread one is downloading a 1MB file while thread two is downloading another 1MB file?

What should be done to get the attention of a thread?

Which of the following definitely indicates that a thread has terminated? I The run method has completed II The method Thread.interrupted returns true III The run method catches an InterruptedException

The sleep method is terminated with a(n) __________ whenever a sleeping thread is interrupted.

What course of action should be followed when a thread has been interrupted?

Which argument(s) present(s) the best case(s) for using the Runnable interface rather than extending the Thread class? I Thread sub-classes are harder to write II Runnable objects can be passed into thread pools III Less time is wasted in creating and destroying thread objects

____ occur(s) if the effect of multiple threads on shared data depends on the order in which the threads are scheduled.

Insert the statement that would start the following thread. Thread firstThread = new Thread(myRunnable) ; ____________________

Each thread runs for a short amount of time, called a ____________________.

In the initial release of the Java library, the Thread class had a stop method to terminate a thread. However, that method is now _______________

Which of the following definitely indicates that a thread has been interrupted by another thread? I The run method has completed II The method Thread.interrupted returns true III The run method catches an InterruptedException

The ____________ occurs when a thread that is not running is interrupted.

The ___________ method does not actually cause threads to terminate; it merely sets a Boolean field in the thread data structure.

A(n) ____ uses a small number of threads to execute a large number of runnables.