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What is the primary purpose of a constructor in Java?

  • To create objects of the class.
  • To define the class methods.
  • To initialize the class variables.
  • To provide a way to destroy objects of the class.
In Java, a constructor's primary purpose is to initialize the class's instance variables when an object is created. Constructors don't define class methods or create/destroy objects; that's not their primary role.
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A ________ block will always execute, whether an exception is thrown or not.

  • catch
  • finally
  • throw
  • try
The finally block is used to define a block of code that always executes, regardless of whether an exception is thrown or not. It's commonly used for cleanup operations such as closing files or releasing resources.
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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.
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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.
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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.
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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.
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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.
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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.
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How can you manipulate request headers when using HttpURLConnection?

  • By altering the HTTP request method
  • By calling addRequestHeader method
  • By modifying the Content-Type header
  • By using the setRequestProperty method
To manipulate request headers in HttpURLConnection, you should use the setRequestProperty method. This method allows you to set custom headers for your HTTP request. Modifying the Content-Type header is one specific use case of this method. The other options are not standard ways to manipulate headers using HttpURLConnection.
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Which of the following is not a valid JDBC transaction isolation level?

  • TRANSACTION_COMMITTED
  • TRANSACTION_NONE
  • TRANSACTION_REPEATABLE_READ
  • TRANSACTION_SERIALIZABLE
JDBC defines standard transaction isolation levels such as TRANSACTION_NONE, TRANSACTION_SERIALIZABLE, and TRANSACTION_REPEATABLE_READ. However, TRANSACTION_COMMITTED is not a valid JDBC transaction isolation level. Isolation levels determine how transactions interact with each other and the data.
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