Imagine you are working on a system that categorizes user feedback into positive, negative, and neutral based on certain keywords. Describe how you'd structure your control statements to efficiently categorize the feedback.
- Create a custom machine learning model
- Implement a decision tree algorithm
- Use if-else statements with keyword checks
- Utilize regular expressions for keyword matching
To efficiently categorize user feedback based on keywords, you can use if-else statements. For each feedback, check if it contains specific positive, negative, or neutral keywords. Regular expressions can also be helpful for more complex matching. While decision trees and machine learning models are powerful for sentiment analysis, they might be overkill for simple keyword-based categorization.
Which of the following access modifiers is allowed for a method in an interface?
- default
- private
- protected
- public
In Java interfaces, all methods are implicitly public, whether you declare them as such or not. You cannot use the private, protected, or default access modifiers for methods in an interface.
Which class allows multiple threads to work in parallel but blocks them until all threads are finished?
- CountDownLatch
- CyclicBarrier
- Semaphore
- ThreadGroup
The CyclicBarrier class allows multiple threads to work in parallel but blocks them until all threads have reached a certain point (barrier) in the code. Once all threads have reached the barrier, they can continue executing. It is commonly used for tasks that can be divided into subtasks that need to be completed before the main task can proceed.
Is it possible to extend a class defined as final?
- No, you cannot extend a class that is declared as final.
- Yes, you can extend a final class.
- You can extend a final class only in the same package.
- You can extend a final class, but it requires special annotations.
In Java, a class declared as "final" cannot be extended. The "final" keyword indicates that the class cannot be subclassed. Attempting to extend a final class will result in a compile-time error. This feature is often used when you want to prevent further modification or extension of a class, such as in utility classes or classes that are critical to the design.
Consider a scenario where you are designing a graphics system that includes different types of shapes (e.g., Circle, Rectangle). How would you decide between using an abstract class and an interface for defining common methods?
- Use a concrete class and use inheritance to define common methods, as concrete classes can directly provide method implementations.
- Use an abstract class with a base shape class and common methods, as abstract classes can provide both method implementations and fields.
- Use an interface to define common methods, as interfaces allow for multiple inheritance and can be implemented by different shape classes.
- Use both an abstract class and an interface, combining the advantages of both.
In this scenario, using an abstract class is appropriate because you can define common methods with default implementations in the base shape class. This provides code reusability and allows shape classes to inherit these methods. Interfaces can also be used, but they don't provide method implementations, making abstract classes a more suitable choice for this use case.
Which searching algorithm requires the data to be sorted to work effectively?
- Binary Search
- Linear Search
- Merge Sort
- Quick Sort
Binary Search is an algorithm that requires the data to be sorted in ascending or descending order for effective searching. It uses the divide and conquer method and is not suitable for unsorted data.
To update UI components from a non-JavaFX thread, use ________.
- Platform.exit()
- Platform.repaint()
- Platform.runLater()
- Platform.update()
To update UI components from a non-JavaFX thread in JavaFX, you should use the Platform.runLater() method. This method allows you to enqueue a Runnable object to be executed on the JavaFX Application Thread, ensuring that UI updates are performed on the correct thread to avoid concurrency issues.
In which scenarios is it recommended to use synchronized blocks instead of synchronized methods?
- When you don't want to use synchronization at all.
- When you want to apply synchronization to a specific section of code within a method, providing more fine-grained control.
- When you want to synchronize an entire method for simplicity.
- When you want to synchronize multiple methods simultaneously.
Synchronized blocks are recommended when you want to apply synchronization to a specific section of code within a method, allowing more fine-grained control over synchronization. This can help reduce contention and improve performance in scenarios where synchronization is necessary. Synchronized methods are used when you want to synchronize the entire method for simplicity.
What is the output of the following code snippet: int[][] arr = new int[3][2]; System.out.println(arr.length);?
- 2
- 3
- 6
- The code will result in a compilation error.
In the given code, arr.length returns the number of rows in the 2D array. Here, arr is declared as a 2D array with 3 rows and 2 columns, so it prints 3, which is the number of rows.
In which sorting algorithm do larger or smaller elements "bubble" to the top of the array?
- Bubble Sort
- Merge Sort
- Quick Sort
- Selection Sort
In Bubble Sort, larger or smaller elements "bubble" to the top of the array as the algorithm repeatedly passes through the list and swaps adjacent elements if they are in the wrong order. The "bubbling" process continues until the entire list is sorted. Bubble Sort is so named due to this bubbling behavior.