Question 1

Suppose thread one is downloading a large file while another thread is processing the same file on a single CPU machine.The time required to download and process a portion of the file is the same.The second thread can process the file while it is incomplete.What is the main benefit of using two threads rather than using a single thread to do both parts of the job?

Accepted Answer

Using two threads allows the processing thread to start working on parts of the file as soon as they are downloaded, making partial results available faster than if a single thread had to wait for the entire download to complete before starting processing.

Question 2

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

Accepted Answer

The sleep method in Java is terminated with an InterruptedException whenever a sleeping thread is interrupted. This exception is thrown to indicate that a thread is waiting, sleeping or doing some other form of sleeping and a thread has interrupted it.

Question 3

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.The second thread can process the file while it is incomplete.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?

Accepted Answer

If we have two CPUs, they can work concurrently on the same file. While one CPU is downloading the file, the other can process the downloaded part of the file. As the downloading and processing rate is the same, the processing thread will be able to keep up with the downloading thread. Therefore, the minimum number of CPUs required is 2. Having more CPUs may further decrease the processing time, but it is not necessary to complete the job in roughly half the time.

Question 4

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

Accepted Answer

Option I can indicate that a thread has completed running, but it doesn't necessarily mean that it was interrupted. Option II indicates that the thread was interrupted, as the Thread.interrupted method is used to check if the thread has been interrupted. And option III also indicates that the thread was interrupted, as the InterruptedException is thrown when a thread is interrupted. Therefore, options II and III are the best choice for indicating that a thread has been interrupted.

Question 5

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

Accepted Answer

The interrupt() method sets a Boolean flag in the thread data structure to indicate that the thread should be interrupted. It does not actually stop the thread's execution; it is up to the thread to check the interrupt flag and respond appropriately. The other methods listed either stop the thread completely (stop()) or suspend it for a specified period (sleep()) or until a condition is met (await()).

Question 6

What happens if we try to start a thread with an instance of a Runnable class that did not override the run method?

Accepted Answer

The inherited run method from the Runnable interface will be executed, which does nothing by default. There will be no compilation errors or exceptions thrown.

Question 7

Which of the following is a characteristic of threads?

Accepted Answer

The order of execution of parallel threads is somewhat random because it depends on the thread scheduler and other factors such as thread priority and availability of resources. The other options (B, C, and D) are not true for threads. Threads may be interleaved, but not in an exact sequence as mentioned in option B. The thread scheduler may execute threads in a different order than its call, depending on the priority and availability of resources. Finally, parallel threads may overlap in time but not necessarily run exactly at the same time and in the same order as mentioned in option D.

Question 8

Suppose that the class XYZ implements the interface Runnable.Which code creates a thread object and makes it available to the scheduler to be executed?

Accepted Answer

The answer of Suppose that the class XYZ implements the...

Question 9

Given that a new thread named t has been constructed, how can you make multiple threads run parallel to each other?

Accepted Answer

The correct method to start a new thread and make it run parallel to other threads is by using the method start(), not run(). The other options (C and D) are not valid methods for creating or running threads.

Question 10

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.The second thread can process the file while it is incomplete.How many total time slices will it take for the first 10 KB to be downloaded and processed?

Accepted Answer

Since each time slice allows 10KB to be either downloaded or processed, both threads will be able to use the CPU in each time slice. Therefore, the first 10KB will take two total time slices: one for the first thread to download 10KB and another for the second thread to process 10KB of the incomplete file.

Question 11

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

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

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

Accepted Answer

The primary advantage of extending the Thread class directly is the ability to execute independently, as each instance of a Thread subclass represents a separate thread of execution. Arguments II and III are incorrect; Runnable objects do not inherently waste more system resources, and there is no inherent speed advantage of Thread subclasses over Runnable objects on a single CPU.

Question 13

What is the difference between calling the sleep method versus the await method?

Accepted Answer

The sleep method pauses the current thread for a set time, while the await method allows the current thread to continue executing other tasks while waiting for the awaited task to complete. Additionally, the await method is used with asynchronous programming while the sleep method can be used for both synchronous and asynchronous programming. Therefore, option B is the correct choice as it correctly distinguishes between the two methods. Option A is incorrect as it confuses the behaviors of the two methods. Option C is incorrect as it does not give enough information to differentiate between the two methods. Option D is incorrect as it claims both methods are the same, which is false.

Question 14

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

Accepted Answer

InterruptedException occurs when a thread that is not running is interrupted, typically by calling the interrupt() method on a thread object. This exception is often used to gracefully stop a thread that is blocked or waiting for a resource.

Question 15

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

Accepted Answer

A thread pool uses a small number of threads to execute a large number of runnables in an efficient and controlled manner. This helps prevent the system from being overloaded by limiting the number of threads running at any given time. A race condition occurs when two or more threads access shared data and attempt to modify it at the same time, leading to unpredictability and errors. A condition object is used to enable threads to wait for a specific condition to be met before continuing execution. Embedded systems are specialized computer systems designed for specific tasks and environments, often with limited resources.

Question 16

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

Accepted Answer

The completion of the run method is the only definite indication that a thread has terminated. While Thread.interrupted returning true or the run method catching an InterruptedException may suggest that a thread has terminated, they do not definitively indicate the thread has completed its execution.

Question 17

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

Accepted Answer

The stop method is deprecated, which means it is no longer recommended and may be removed in future versions of Java. It is unsafe to use because it can leave an object in an inconsistent state, potentially leading to unexpected behavior. It is recommended to use other thread control mechanisms, such as interrupt or a shared variable, to gracefully stop a thread.

Question 18

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

Accepted Answer

Calling the interrupt method on a thread will cause it to throw an InterruptedException, which can be caught and handled accordingly. This can be used as a way to get the attention of a running thread without forcefully stopping its execution.

Question 19

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.The second thread can process the file while it is incomplete.How many total time slices will it take to process half the file?

Accepted Answer

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

Question 20

A program that creates a large number of short-lived threads can be inefficient in memory and time.Which of the following can reduce the cost of using threads?

Accepted Answer

A thread pool can manage a group of threads, reusing them as needed, which can reduce the overhead of creating and destroying threads for each task. This can make the use of threads more efficient in terms of both memory and time.

Quiz 22: Multithreading