How does the invokeAll() method of ExecutorService behave?
- It executes all submitted tasks concurrently and returns a list of Future objects representing their results.
- It executes all submitted tasks concurrently and returns the result of the first task that completes successfully.
- It submits all tasks to the ExecutorService but returns only the first completed task's result.
- It waits indefinitely until all tasks are completed, returning the results in the order they were submitted.
The invokeAll() method of ExecutorService takes a collection of Callable tasks, executes them concurrently, and returns a list of Future objects that represent the results. The order of the results matches the order of the tasks in the input collection. It doesn't return results as they complete; it waits for all tasks to finish and then returns the results.
The ________ keyword is used to provide the default implementation of a method declared in an interface.
- default
- define
- extend
- implement
In Java, the default keyword is used to provide a default implementation of a method declared in an interface. This allows the interface to evolve over time without breaking the existing implementing classes. The default keyword signifies that the method has a default implementation in the interface. The other options are not used for this purpose.
The expression x *= 3 is equivalent to x = x ______ 3.
- %
- +
- -
- /
The expression x *= 3 is equivalent to x = x * 3. Therefore, the operator that belongs in the blank is *. This operator multiplies x by 3 and assigns the result back to x. It's known as the multiplication assignment operator.
Consider a scenario where you need to build a Java application that periodically checks a set of URLs to ensure they are accessible. How would you manage the connections and which classes/methods might be useful to achieve this efficiently?
- Employ the java.util.TimerTask class to create a periodic task. Handle connections with java.io.InputStream and java.io.OutputStream.
- Use the java.io.BufferedWriter and java.io.BufferedReader classes for URL handling. Implement periodic checks using Thread.sleep() and custom thread management.
- Use the java.net.URL class to represent URLs and java.net.HttpURLConnection class to open connections. Implement a periodic task using ScheduledExecutorService to make HTTP requests.
- Utilize the java.net.Socket class for low-level socket operations. Employ Timer class to schedule periodic checks.
To efficiently manage connections to URLs in a Java application, you can use the java.net.URL class to represent the URLs and the java.net.HttpURLConnection class to open connections to these URLs. To perform periodic checks, you can utilize ScheduledExecutorService to create a scheduled task that makes HTTP requests at specified intervals. This approach allows for efficient URL checking and connection management.
What is the average-case time complexity of Binary Search?
- O(1)
- O(log n)
- O(n log n)
- O(n)
The average-case time complexity of Binary Search is O(log n), where 'n' is the number of elements in the array. This is because, on average, Binary Search eliminates half of the remaining elements with each comparison, resulting in a logarithmic growth rate. In the worst-case, it is still O(log n), but in the best-case, it can be O(1) as mentioned in the first question.
What will be the result of the expression 7 ^ 3 in Java?
- 0
- 10
- 3
- 4
In Java, the ^ operator is the bitwise XOR operator. It performs a bitwise XOR operation on the binary representations of the two operands. In this case, 7 in binary is 0111, and 3 in binary is 0011. Performing XOR, we get 0100, which is 4 in decimal. So, the result is 4.
Can method overloading be achieved by changing only the return type of methods?
- No, method overloading can only be achieved by changing both the method name and return type.
- No, method overloading is not possible by changing only the return type; the method name and/or parameters must also differ.
- Yes, as long as the method name and parameters are the same, changing the return type is sufficient for method overloading.
- Yes, method overloading can be achieved solely by changing the return type, even if the method name and parameters are the same.
Method overloading is based on the method name and parameters, not the return type. Therefore, simply changing the return type of methods with the same name and parameters does not constitute method overloading in Java. Different parameters are required to overload methods.
The ______ class in JavaFX is used to create a simple timeline animation.
- AnimationTimer
- KeyFrame
- Timeline
- TranslateTransition
In JavaFX, the Timeline class is used to create a simple timeline animation. It allows you to define keyframes and specify changes in properties over time, making it suitable for animations. The other options are also related to animations but serve different purposes.
The ________ Interface extends Collection and declares the behavior of containers
- Iterable
- List
- Map
- Queue
The List interface extends the Collection interface in Java. It is used to represent ordered collections of elements, allowing duplicates and providing various methods to manipulate the list. The other options do not extend Collection.
In a situation where you are developing a caching solution that needs fast retrieval and insertion of key/value pairs but also needs to maintain insertion order for iteration, which Map implementation would be most suitable?
- HashMap
- Hashtable
- LinkedHashMap
- TreeMap
For a caching solution requiring fast retrieval, insertion, and maintaining insertion order, LinkedHashMap is the most suitable choice. It combines the features of a hash table and a linked list, allowing for constant-time retrieval and insertion while also preserving the order of insertion. HashMap offers fast retrieval but doesn't guarantee order. TreeMap orders elements but has a more complex structure. Hashtable is outdated and should be avoided.