You are developing a payroll system. How would you design a class for storing employee details and ensuring that some sensitive information (like salary) cannot be accessed directly from the object?
- Define private instance variables for employee details, including salary, and provide public get and set methods for accessing and modifying the salary.
- Define public instance variables for employee details and make the salary variable final.
- Define public static variables for employee details, including salary, and use the 'protected' access modifier.
- Use the 'volatile' keyword for sensitive information like salary.
To ensure that sensitive information like salary cannot be accessed directly from the object, you should define private instance variables for employee details and provide public get and set methods for salary. This follows the principle of encapsulation, which restricts direct access to sensitive data. The other options do not provide adequate security for sensitive information.
Consider a case where you have to model a "Book" in a library system. What properties and methods would you define in the Book class and why?
- Properties: name, genre, pages; Methods: play, pause, stop.
- Properties: title, author, ISBN, publication date; Methods: get and set methods for properties, toString for representation.
- Properties: title, author, ISBN; Methods: checkAvailability, reserve, extendDueDate.
- Properties: title, author, publication date; Methods: borrow, return, calculateFine.
In a Book class for a library system, you would define properties like title, author, ISBN, and publication date as they represent essential book attributes. Get and set methods are used for encapsulation and data integrity, and the toString method helps in displaying the book's details. The other options include irrelevant properties and methods.
Which of the following is a key characteristic of a lambda expression in Java?
- It can capture local variables.
- It can have multiple methods.
- It is a data type.
- It is an anonymous inner class.
A key characteristic of a lambda expression in Java is that it can capture local variables from its enclosing scope. This allows lambda expressions to use values from the surrounding context, making them useful for creating concise and expressive code.
Which method is used to display a stage in JavaFX?
- displayStage()
- openStage()
- primaryStage()
- showStage()
In JavaFX, the show() method is used to display a stage. When you create a JavaFX application, you typically create a Stage object and use its show() method to make it visible. The other options are not valid methods for displaying a stage.
How can CSS be applied to style JavaFX components?
- By attaching external CSS files to the JavaFX application using the addStylesheet() method.
- By calling the applyCSS() method on the entire scene graph.
- By using JavaScript code embedded in the JavaFX application.
- By using the setStyle() method to apply inline CSS directly to individual components.
CSS can be applied to style JavaFX components by attaching external CSS files to the application using the addStylesheet() method. This allows for a separation of concerns between the application logic and its styling. It provides flexibility and maintainability in designing the user interface. Inline CSS can also be used for individual components, but it's not the standard way to style JavaFX applications.
The keyword ________ is used to apply restrictions on class, method, and variable.
- final
- private
- protected
- static
The keyword "private" is used to apply restrictions on class members. It restricts access to only within the same class, making it the most restrictive access modifier in Java.
Which of the following functional interfaces in Java utilizes Lambda expressions?
- AbstractClass
- FunctionalInterface
- Runnable
- Serializable
The Runnable interface in Java can be implemented using lambda expressions. It's a functional interface with a single abstract method run(). This allows you to use lambda expressions for tasks that can be executed concurrently. Lambda expressions simplify the creation of anonymous classes for such tasks.
What will happen if the superclass method does not exist in the subclass while trying to override it?
- It will automatically create a new method in the subclass with the same name.
- It will lead to a compile-time error.
- It will result in a runtime error.
- It will use the superclass method without any issue.
In Java, when you try to override a method from a superclass in a subclass, the method in the superclass must exist; otherwise, it will lead to a compile-time error. Java enforces method signature matching during compile-time, so if the method doesn't exist in the superclass, the compiler will not find a method to override in the subclass, resulting in an error.
The ________ method of Throwable class can be used to retrieve the description of an exception.
- getDescription()
- getDescriptionText()
- getExceptionDescription()
- getMessage()
The getMessage() method of the Throwable class is used to retrieve the description or message associated with an exception. This message provides additional information about the exception, helping developers understand the cause of the error.
Which of the following classes is used to write characters to a file in Java?
- BufferedReader
- FileOutputStream
- FileWriter
- PrintWriter
The FileWriter class in Java is used to write characters to a file. It provides methods to write character data to a file in a character stream. FileOutputStream is used for writing binary data, PrintWriter is used for formatted text output, and BufferedReader is used for reading character data, not writing.