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In this code, an ExecutorService is created with a fixed thread pool of size 2 using Executors.newFixedThreadPool(2). A Runnable task is defined to print "Task is complete" to the console.

The sequence of operations is as follows:

service.submit(task);

This submits the task to the executor service for execution. Since the thread pool has a size of 2 and no other tasks are running, this task will be executed promptly, printing "Task is complete" to the console.

service.shutdown();

This initiates an orderly shutdown of the executor service. In this state, the service stops accepting new tasks

In Java, the ConcurrentHashMap class provides several constructors that allow for the customization of its initial capacity, load factor, and concurrency level. To configure a ConcurrentHashMap with an initial capacity of 42 and a concurrency level of 10, you can use the following constructor:

java

public ConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel)

Parameters:

initialCapacity: The initial capacity of the hash table. This is the number of buckets that the hash table will have when it is created. In this case, it is set to 42.

loadFactor: A measure of how full the hash table is allowed to get before it is resized. The default value is 0.75, but in this case, it is set to 0.88.

concurrencyLevel: The estimated number of concurrently updating threads. This is used as a hint for internal sizing. In this case, it is set to 10.

Therefore, to create a ConcurrentHashMap with an initial capacity of 42, a load factor of 0.88, and a concurrency level of 10, you can use the following code:

java

var concurrentHashMap = new ConcurrentHashMap<>(42, 0.88f, 10);

Option Evaluations:

A. var concurrentHashMap = new ConcurrentHashMap(42);: This constructor sets the initial capacity to 42 but uses the default load factor (0.75) and concurrency level (16). It does not meet the requirement of setting the concurrency level to 10.

B. None of the suggestions.: This is incorrect because option E provides the correct configuration.

C. var concurrentHashMap = new ConcurrentHashMap();: This uses the default constructor, which sets the initial capacity to 16, the load factor to 0.75, and the concurrency level to 16. It does not meet the specified requirements.

D. var concurrentHashMap = new ConcurrentHashMap(42, 10);: This constructor sets the initial capacity to 42 and the load factor to 10, which is incorrect because the load factor should be a float value between 0 and 1.

E. var concurrentHashMap = new ConcurrentHashMap(42, 0.88f, 10);: This correctly sets the initial capacity to 42, the load factor to 0.88, and the concurrency level to 10, meeting all the specified requirements.

Therefore, the correct answer is option E.

In this program, the following operations are performed:

Paths Initialization:

Path p1 is set to "f1.txt".

Path p2 is set to "f2.txt".

File Move Operation:

Files.move(p1, p2); attempts to move (or rename) f1.txt to f2.txt.

File Delete Operation:

Files.delete(p1); attempts to delete f1.txt.

Analysis:

If f1.txt Does Not Exist:

The Files.move(p1, p2); operation will throw a NoSuchFileException because the source file f1.txt is missing.

If f1.txt Exists and f2.txt Does Not Exist:

The Files.move(p1, p2); operation will successfully rename f1.txt to f2.txt.

Subsequently, the Files.delete(p1); operation will throw a NoSuchFileException because p1 (now f1.txt) no longer exists after the move.

If Both f1.txt and f2.txt Exist:

The Files.move(p1, p2); operation will throw a FileAlreadyExistsException because the target file f2.txt already exists.

If f2.txt Exists While f1.txt Does Not:

Similar to the first scenario, the Files.move(p1, p2); operation will throw a NoSuchFileException due to the absence of f1.txt.

In all possible scenarios, an exception is thrown during the execution of the program.

In this code, a TreeSet named frenchCities is created and populated with the following cities: "Paris", "Marseille", "Lyon", "Lille", and "Toulouse". The TreeSet class in Java stores elements in a sorted order according to their natural ordering, which, for strings, is lexicographical order.

Sorted Order of Elements:

When the elements are added to the TreeSet, they are stored in the following order:

"Lille"

"Lyon"

"Marseille"

"Paris"

"Toulouse"

headSet Method:

The headSet(E toElement) method of the TreeSet class returns a view of the portion of this set whose elements are strictly less than toElement. In this case, frenchCities.headSet("Marseille") will return a subset of frenchCities containing all elements that are lexicographically less than "Marseille".

Elements Less Than "Marseille":

From the sorted order, the elements that are less than "Marseille" are:

"Lille"

"Lyon"

Therefore, the output of the System.out.println statement will be [Lille, Lyon].

Option Evaluations:

A. [Paris]: Incorrect. "Paris" is lexicographically greater than "Marseille".

B. [Paris, Toulouse]: Incorrect. Both "Paris" and "Toulouse" are lexicographically greater than "Marseille".

C. [Lille, Lyon]: Correct. These are the elements less than "Marseille".

D. Compilation fails: Incorrect. The code compiles successfully.

E. [Lyon, Lille, Toulouse]: Incorrect. "Toulouse" is lexicographically greater than "Marseille".

In this code, the try block throws an IOException. The catch block catches this exception and throws a new RuntimeException. Regardless of exceptions thrown in the try or catch blocks, the finally block is always executed. In this case, the finally block throws an ArithmeticException.

When an exception is thrown in a finally block, it overrides any previous exceptions that were thrown in the try or catch blocks. Therefore, the ArithmeticException thrown in the finally block is the exception that propagates out of the method. As a result, the program terminates with an ArithmeticException.

Analyzing the thrower() Method Execution

java

int i = 0;

return i / i;

i / i evaluates to 0 / 0, whichthrows ArithmeticException (/ by zero).

Since catch (NumberFormatException e) doesnot matchArithmeticException, it is skipped.

The finally block always executes, printing:

nginx

Beaujolais Nouveau,

The exceptionpropagates backto main().

Handling the Exception in main()

java

try {

thrower();

System.out.print("Dom Pérignon, ");

} catch (Exception e) {

System.out.print("Chablis, ");

} finally {

System.out.print("Saint-Émilion");

}

Since thrower() throws ArithmeticException, it is caught by catch (Exception e).

"Chablis, "is printed.

Thefinally block always executes, printing "Saint-Émilion".

Final Output

nginx

Beaujolais Nouveau, Chablis, Saint-Émilion

Thus, the correct answer is:Beaujolais Nouveau, Chablis, Saint-Émilion

References:

Java SE 21 - Exception Handling

Java SE 21 - finally Block Execution

In this code, a list of integers integers is created containing the elements 0, 1, and 2. A stream is then created from this list, and the following operations are performed in sequence:

peek(System.out::print):

The peek method is an intermediate operation that allows performing an action on each element as it is encountered in the stream. In this case, System.out::print is used to print each element. However, since peek is intermediate, the printing occurs only when a terminal operation is executed.

limit(2):

The limit method is another intermediate operation that truncates the stream to contain no more than the specified number of elements. Here, it limits the stream to the first 2 elements.

forEach(i -> {}):

The forEach method is a terminal operation that performs the given action on each element of the stream. In this case, the action is an empty lambda expression (i -> {}), which does nothing for each element.

The sequence of operations can be visualized as follows:

Original Stream Elements: 0, 1, 2

After peek(System.out::print): Elements are printed as they are encountered.

After limit(2): Stream is truncated to 0, 1.

After forEach(i -> {}): No additional action; serves to trigger the processing.

Therefore, the output of the code is 01, corresponding to the first two elements of the list being printed due to the peek operation.

In this code, three static methods from the Boolean class are used: logicalAnd, logicalOr, and logicalXor. Each method takes two boolean arguments and returns a boolean result based on the respective logical operation.

Evaluation of Each Statement:

Boolean.logicalAnd(1 == 1, 2 < 1)

Operands:

1 == 1 evaluates to true.

2 < 1 evaluates to false.

Operation:

Boolean.logicalAnd(true, false) performs a logical AND operation.

The result is false because both operands must be true for the AND operation to return true.

Output:

System.out.print(false); prints false.

Boolean.logicalOr(1 == 1, 2 < 1)

Operands:

1 == 1 evaluates to true.

2 < 1 evaluates to false.

Operation:

Boolean.logicalOr(true, false) performs a logical OR operation.

The result is true because at least one operand is true.

Output:

System.out.print(true); prints true.

Boolean.logicalXor(1 == 1, 2 < 1)

Operands:

1 == 1 evaluates to true.

2 < 1 evaluates to false.

Operation:

Boolean.logicalXor(true, false) performs a logical XOR (exclusive OR) operation.

The result is true because exactly one operand is true.

Output:

System.out.print(true); prints true.

Combined Output:

Combining the outputs from each statement, the final printed result is:

nginx

falsetruetrue

Understanding ExecutorService Methods

execute(Runnable command)

Runs the task but only supports Runnable (not Callable).

❌execService.execute(task2); fails because task2 is Callable.

submit(Runnable task)

Submits a Runnable task for execution.

execService.submit(task1); executes "Executing Task-1".

submit(Callable<T> task)

Submits a Callable task for execution.

execService.submit(task2); executes "Executing Task-2".

call() Does Not Exist in ExecutorService

❌execService.call(task1); and execService.call(task2); are invalid.

run() Does Not Exist in ExecutorService

❌execService.run(task1); and execService.run(task2); are invalid.

Correct Code to Print Both Messages:

java

execService.submit(task1);

execService.submit(task2);

Thus, the correct answer is:execService.submit(task1); execService.submit(task2);

References:

Java SE 21 - ExecutorService

Java SE 21 - Callable and Runnable

Understanding CopyOnWriteArrayList

CopyOnWriteArrayList is a thread-safe variant of ArrayList whereall mutative operations (add, set, remove, etc.) create a new copy of the underlying array.

This meansiterations will not reflect modifications made after the iterator was created.

Instead of modifying the existing array, a new copy is created for modifications, ensuring that readers always see a consistent snapshot.

Thread Execution Behavior

Thread 1 (Writer Thread)adds "D" to the list.

Thread 2 (Reader Thread)iterates over the list.

The reader thread gets a snapshot of the listbefore"D" is added.

The output may look like:

mathematica

Read element: A

Read element: B

Read element: C

Element added: D

"D" may not appear in the output of the reader threadbecause the iteration occurs on a snapshot before the modification.

Why doesn't it print all elements including changes?

Since CopyOnWriteArrayList doesnot allow changes to be visible during iteration, the reader threadwill not see "D"if it started iterating before "D" was added.

Thus, the correct answer is:"It prints all elements, but changes made during iteration may not be visible."

References:

Java SE 21 - CopyOnWriteArrayList