When reading from a file using a FileReader, it's often wrapped with a ________ to increase efficiency.
- BufferedReader
- FileBufferReader
- FileWriter
- InputStreamReader
When reading from a file, wrapping a FileReader with a BufferedReader is a common practice in Java. BufferedReader buffers the input, reducing the number of reads from the file and thus increasing efficiency.
Which of the following data structures does not allow duplicate elements?
- ArrayList
- HashSet
- LinkedList
- TreeMap
The HashSet data structure in Java does not allow duplicate elements. It is implemented using a hash table and ensures that all elements are unique by using the hashing mechanism. ArrayList and LinkedList can contain duplicate elements, while TreeMap allows duplicates based on keys.
What will be the output of the executeQuery() method in JDBC?
- A boolean indicating success or failure.
- Nothing; it doesn't return any value.
- The number of rows affected.
- The result of the SQL query execution.
The executeQuery() method in JDBC returns a ResultSet object, which contains the result of the SQL query execution. This ResultSet can be used to retrieve and manipulate the query results. The other options are incorrect as they do not accurately describe the output of this method.
The ________ class provides a tunable, flexible thread pool.
- ExecutorService
- Runnable
- Thread
- ThreadPoolExecutor
The ThreadPoolExecutor class in Java provides a tunable, flexible thread pool. It allows you to customize various aspects of thread pool behavior, such as the number of threads and task scheduling.
How does the BufferedOutputStream class work in Java when connected to a file output byte stream?
- It compresses the data before writing it to the file stream to save storage space.
- It encrypts the data to provide security during the write operation.
- It improves I/O performance by reducing the number of write operations to the underlying stream.
- It reads data from the file output stream and stores it in a buffer for later retrieval.
BufferedOutputStream in Java enhances performance by buffering the output data before writing it to the underlying file stream. This reduces the number of write operations and improves efficiency. It doesn't read or compress data; its primary purpose is to optimize data output.
How can we gracefully shutdown an ExecutorService?
- Call shutdown()
- Call shutdown() and then shutdownNow()
- Call shutdownNow() and then shutdown()
- Call stop()
To gracefully shut down an ExecutorService, you should first call the shutdown() method, which initiates an orderly shutdown, allowing previously submitted tasks to execute before terminating. You should not call shutdownNow() before shutdown() because it forcefully attempts to stop all executing tasks. The other options are incorrect for a graceful shutdown.
Imagine you are implementing a system that performs various mathematical operations. How would you use Lambda expressions to define various operations in a clean and efficient way?
- By creating a separate class for each mathematical operation and using the Lambda keyword to instantiate objects of these classes.
- By defining functional interfaces with abstract methods corresponding to each mathematical operation and implementing them using Lambda expressions.
- By using nested Lambda expressions within each other to perform mathematical operations.
- By using traditional method declarations and avoiding Lambda expressions for mathematical operations.
In Java, you can use Lambda expressions to implement functional interfaces with a single abstract method. For mathematical operations, you can define functional interfaces, such as BinaryOperator, and use Lambda expressions to implement these interfaces concisely and efficiently. This approach enhances code readability and allows you to pass behavior as data, making your code more modular.
Can we override a method in the same class?
- No, it is not allowed
- Yes, but it has no practical purpose
- Yes, it is allowed
- Yes, with different method names
In Java, method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. Therefore, it is not possible to override a method in the same class because there is no superclass-subclass relationship. However, you can overload methods within the same class by defining methods with the same name but different parameter lists.
The ________ parameter allows Lambda expressions to be passed around as if it was a type.
- Consumer
- Functional
- Predicate
- Target
The term you're looking for is "Functional." In Java, Lambda expressions can be assigned to functional interfaces, which act as a type for lambda expressions. These interfaces typically define a single abstract method that the lambda expression implements. This allows lambda expressions to be treated as if they were a type, and they can be passed as parameters to methods, returned from methods, or stored in variables.
In a scenario where you are developing a JavaFX application with multiple scenes and want to preserve the state when switching between these scenes, how would you manage and transfer data between them?
- Serialize the data objects and pass them as parameters when loading new scenes.
- Store data in global variables within the main application class and access them directly from different scenes.
- Use Java's File class to write data to disk and read it back when switching between scenes.
- Use a centralized data model or service to store and share data between scenes, ensuring data consistency.
To manage and transfer data between scenes in a JavaFX application, it's best to use a centralized data model or service. This approach ensures data consistency and makes it easier to share data between different scenes. Serializing data objects, global variables, and file operations are less suitable for preserving data between scenes.