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 methods can be used to create a stream from a collection?
- filter()
- forEach()
- mapToDouble()
- stream()
You can create a stream from a collection in Java using the stream() method. This method is available on all collections and provides a way to obtain a stream that allows you to perform various stream operations on the elements of the collection. Options 2 to 4 are not used to create streams but for other stream operations.
What is the difference between a synchronized block and a synchronized method?
- Synchronized blocks are used for asynchronous programming.
- Synchronized blocks can be used to synchronize multiple sections of code within the same method.
- Synchronized methods are more efficient than synchronized blocks.
- Synchronized methods can only be used to synchronize the entire method.
The key difference between a synchronized block and a synchronized method is that synchronized blocks can be used to synchronize multiple sections of code within the same method, providing more fine-grained control over synchronization. In contrast, synchronized methods synchronize the entire method. Synchronized methods are not necessarily more efficient than synchronized blocks; their efficiency depends on the specific use case.
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.
What happens if no constructor is provided in a Java class?
- The class cannot be instantiated, and objects of that class cannot be created.
- Java automatically provides a default no-argument constructor for the class.
- The class can only be instantiated by other classes in the same package.
- The class becomes a singleton by default.
a) is correct. If no constructor is provided in a Java class, Java automatically provides a default no-argument constructor. b) is a common misconception; Java only provides a default constructor if you haven't defined any constructors explicitly. c) and d) are incorrect statements.
The ________ method of the String class returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
- indexOf(char ch)
- indexOf(char ch, int fromIndex)
- lastIndexOf(char ch)
- lastIndexOf(char ch, int fromIndex)
The lastIndexOf(char ch, int fromIndex) method of the String class is used to find the index of the last occurrence of the specified character within the string, starting the search from the given index fromIndex. The other options are related to the indexOf method but don't perform the same task.