________ is a special type of statement, which is used to invoke a constructor of the same class.
- Create
- Instantiate
- Super
- This
The "this" keyword in Java is used to refer to the current instance of a class. When used as a statement, "this" is used to invoke the constructor of the same class. This makes option 4 ("This") the correct choice.
A custom exception can be thrown using the ________ keyword followed by an object of the custom exception.
- create
- initiate
- raise
- throw
In Java, a custom exception can be thrown using the throw keyword followed by an object of the custom exception class. This allows you to handle specific exceptional situations that may not be covered by built-in exceptions. It's an essential part of creating robust and specialized exception handling in Java applications.
Which method is used to execute SQL queries in JDBC?
- executeQuery()
- executeSQL()
- executeStatement()
- executeUpdate()
The executeQuery() method in JDBC is used to execute SQL queries that return a ResultSet, typically used for SELECT statements. The executeUpdate() method is used for executing SQL queries that modify the database, such as INSERT, UPDATE, or DELETE statements. The other options mentioned are not valid JDBC methods.
You are tasked with developing a system where the order of elements matters and you have frequent insertions and deletions. Which List implementation would be preferable and why?
- ArrayList
- HashSet
- LinkedList
- Vector
In a scenario with frequent insertions and deletions where the order of elements matters, a LinkedList is preferable. LinkedList offers efficient insertions and deletions because it doesn't require shifting elements like ArrayList. Vector is a synchronized version of ArrayList and might introduce unnecessary synchronization overhead if not needed. HashSet is not a List implementation and doesn't preserve order.
What is the purpose of the start() method in a JavaFX application?
- It defines the application's GUI components.
- It handles user input events.
- It initializes the application's resources.
- It is the entry point for launching the app.
The start() method is the entry point for a JavaFX application. It is automatically called by the JavaFX framework when the application starts. Within this method, you set up the initial state of your application, create the main user interface, and configure event handling. This method serves as the starting point for building your JavaFX application.
Can an abstract class have a constructor in Java?
- It depends on the class
- No
- Yes, always
- Yes, but with restrictions
Yes, an abstract class can have a constructor in Java. However, there are some restrictions. The constructor of an abstract class is typically used to initialize the fields of the abstract class, and it can be called from subclasses using the super keyword.
Consider a scenario where multiple threads are executing tasks, but the main thread needs to wait until all tasks are complete before proceeding. How can this be achieved using Future and ExecutorService?
- Use ExecutorService's awaitTermination() method to block the main thread until all tasks are completed.
- Use ExecutorService's invokeAny() method to submit tasks and block the main thread until any one of the tasks completes.
- Use ExecutorService's shutdown() method to ensure that all tasks are complete before proceeding with the main thread.
- Use invokeAll() method of ExecutorService to submit tasks and obtain a list of Future objects, then call get() method on each Future object to block the main thread until tasks are complete.
In this scenario, you can use the invokeAll() method to submit tasks and obtain a list of Future objects representing each task. Calling the get() method on each Future object will block the main thread until all tasks are complete. This allows synchronization between the main thread and the worker threads.
A thread enters the ________ state once its run() method has completed execution.
- Blocked
- Runnable
- Terminated
- Waiting
A thread enters the "Terminated" state in Java once its "run()" method has completed execution. In this state, the thread has finished its task and is no longer actively executing code.
You are building a text editor in Java which reads large text files. How would you utilize character streams to read data from files, and why are character streams preferable in this scenario?
- Use BufferedReader and BufferedWriter to create character streams, as they read and write character data in chunks.
- Use FileInputStream and FileOutputStream to create character streams, as they can handle character data efficiently.
- Use FileReader and FileWriter to create character streams, as they provide direct access to character data.
- Use ObjectOutputStream and ObjectInputStream to create character streams, as they can serialize character objects.
In the context of a text editor reading large text files, using BufferedReader and BufferedWriter is preferable. These classes efficiently read and write character data in chunks, reducing the I/O overhead and improving performance. FileInputStream/FileOutputStream deal with bytes, FileReader/FileWriter are less efficient for large files, and ObjectOutputStream/ObjectInputStream are for object serialization.
Consider a scenario where you have to develop a JavaFX application that should adapt to different screen sizes. How would you approach the design and layout to ensure that the application is responsive and the UI adjusts dynamically?
- Create separate layouts for each screen size and switch between them based on the detected screen size.
- Set fixed pixel sizes for all UI elements to ensure consistent appearance across different screen sizes.
- Use JavaFX layout containers like VBox and HBox along with percentage-based sizing and responsive design principles.
- Use absolute positioning for UI elements to maintain precise control over their placement.
To create a responsive JavaFX application, you should use layout containers like VBox and HBox and design with percentage-based sizing to allow elements to adjust dynamically. Responsive design principles are essential for accommodating various screen sizes. Fixed pixel sizes, separate layouts, and absolute positioning are not recommended for achieving responsiveness.