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.
How does the "diamond problem" get resolved in Java while using interfaces?
- In Java, the "diamond problem" cannot be resolved, and it leads to a compilation error.
- Java resolves the "diamond problem" by allowing classes to implement multiple interfaces with conflicting method signatures.
- The "diamond problem" is resolved by introducing explicit casting to specify which method to call when there is a conflict.
- The "diamond problem" is resolved by renaming the conflicting methods in the implementing class.
In Java, the "diamond problem" occurs when a class inherits from two or more classes that have a common ancestor with a method of the same name. To resolve this, Java allows classes to implement multiple interfaces with conflicting method signatures. This forces the implementing class to provide its own implementation, and it must explicitly call the desired method using the interface name.
A two-dimensional array int[][] arr is essentially an array of ________ in Java.
- arrays
- arrays of arrays
- arrays of integers
- integers
In Java, a two-dimensional array int[][] arr is essentially an array of arrays. It means that each element of arr is itself an array, which can hold integers or other data types. This concept allows you to create tables or matrices of data.
The _______ block in a Java class is executed before constructors.
- finalize
- instance
- main
- static
In Java, the static block is executed before constructors. Static blocks are used for performing class-level initialization tasks. They run when the class is loaded, and they are executed only once. Constructors, on the other hand, are used to initialize instance variables and are called when an object is created.
What is the purpose of the flatMap() method in the Stream API?
- To collect the elements of the stream into a list
- To filter elements based on a given predicate
- To flatten a stream of streams into a single stream
- To perform an operation on each element in the stream
The flatMap() method in the Stream API is used to flatten a stream of streams into a single stream. It is particularly useful when you have a stream of elements, and each element is itself a stream (e.g., a stream of lists). flatMap() will merge all these sub-streams into one, providing a single stream of elements. This is different from map(), which produces a stream of streams.