Question 1

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 Thread.stop() method is deprecated, which means it should no longer be used in new code and should be replaced by other means of terminating a thread. This is due to the fact that the method can cause various problems like leaving resources in an inconsistent state, which could lead to unexpected behavior or security vulnerabilities. It is recommended to use more appropriate methods like interrupt() or a shared boolean flag to terminate a thread in a controlled and safe manner.

Question 2

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

While runnable objects can be more efficient and scalable in certain situations, creating a new thread subclass allows for more control over the thread's behavior and can guarantee independent execution. Arguments II and III are not necessarily true and depend on the specific implementation.

Question 3

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

To start a thread, we need to call the start() method on the thread object. Therefore, the correct statement to start the thread would be firstThread.start(). Option A is incorrect because calling the run() method directly on the thread object will not start a new thread, but rather executes the code in the same thread as the caller. Options C and D are also incorrect as they do not refer to the thread object correctly.

Question 4

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 answer of What course of action should be followed...

Question 5

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 designed to use a small number of threads to execute a large number of runnables. This can help to improve the efficiency of a program by reusing threads instead of creating new ones for each task.

Question 6

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 7

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

When a thread is interrupted by another thread, the interrupted status of the thread is set to true. This can be detected in three ways:
I. The run method may complete normally without any indication of interruption.
II. The method Thread.interrupted can be called to check the interrupted status of a thread. This method returns true if the thread was interrupted; otherwise, it returns false and clears the interrupted status.
III. A method may catch an InterruptedException, which is thrown when a thread is waiting, sleeping or otherwise blocked and is interrupted by another thread. Thus, options II and III definitely indicate that a thread has been interrupted by another thread. Option I, on the other hand, may or may not indicate interruption, as the run method may complete normally without interruption.

Question 8

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 stop whatever it is doing and throw an InterruptedException, allowing it to be handled or terminated gracefully. This is a safer and more effective way of getting a thread's attention compared to the other options.

Question 9

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, an InterruptedException is thrown to indicate that the sleep has been prematurely terminated.

Question 10

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 used to describe the short amount of time that a thread runs for is a "time slice." While options A, B, and D all contain elements of this concept, "time slice" is the most commonly used term in computer science literature.

Question 11

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 12

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 flag that indicates whether the thread has been interrupted. It does not actually stop the thread, but rather sets a flag to be checked by the thread, allowing it to gracefully terminate on its own.

Question 13

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

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

Question 14

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 15

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

The answer of Suppose thread one is downloading a large...

Question 16

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

Option II is a major reason to use Runnable interface as it allows objects to be submitted to thread pools which can be managed and reused efficiently. Option III is also a valid point because creating and destroying thread objects is an expensive process, and using Runnable interface avoids this overhead. Option I is not necessarily true for everyone and may depend on individual coding skills. Therefore, C is the best choice as it covers the primary benefits of using the Runnable interface.

Question 17

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

Accepted Answer

The InterruptedException is thrown when a thread is waiting, sleeping, or otherwise occupied, and the thread is interrupted, either before or during its activity. This indicates that the thread should stop what it's doing and terminate.

Question 18

____ 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

Race conditions occur when multiple threads access and modify shared data simultaneously and the final outcome of the data depends on the order in which the threads are executed. This can lead to unexpected results and errors in the program.

Question 19

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

Option I is the definite indicator of a thread terminating as it indicates that the run method, which is the entry point of the thread, has completed. 
Option II is not a definite indicator, as Thread.interrupted() method can also return true if the thread is interrupted but continues running, and it does not necessarily mean that the thread has terminated. 
Option III indicates that the thread has been interrupted and is no longer waiting or sleeping; however, it does not necessarily mean that the thread has terminated.

Question 20

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

With a single CPU, the total time taken to download and process the entire file would be:

Time = (800KB / 10KB per slice) * 1 time slice per cycle * 1 CPU cycle per cycle
Time = 80 cycles

With two CPUs, both threads can execute simultaneously, so the total time taken would be roughly half of the single-CPU time:

Time = (800KB / 10KB per slice) * 1 time slice per cycle * 0.5 CPU cycle per cycle
Time = 40 cycles

Therefore, the minimum number of CPUs required to complete the job in roughly half the time of a single-CPU machine is 2.

Quiz 20: Multithreading

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

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

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

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

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

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

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

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

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

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

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

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

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

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