The ________ method of ExecutorService attempts to stop all actively executing tasks and halts the processing of waiting tasks.
- pause()
- shutdown()
- stop()
- terminate()
In Java, the shutdown() method of ExecutorService attempts to stop all actively executing tasks and halts the processing of waiting tasks. It's a graceful way to shut down an executor, allowing it to finish executing tasks before terminating. It is essential to manage thread pools effectively in concurrent applications.
Which of the following statements are true regarding the intern() method of the String class?
- Calling intern() on a String can reduce memory usage by ensuring only one copy exists in the string pool.
- The intern() method adds the String to the string pool.
- The intern() method is only available in Java 9 and later.
- The intern() method returns a new String object.
The intern() method of the String class is used to add the String to the string pool if it's not already there and returns a reference to that String. This can reduce memory usage by ensuring only one copy of a particular string exists in the string pool, which is useful for memory optimization. The intern() method has been available since early versions of Java, not just in Java 9 and later.
Consider a scenario where a very large number of string concatenation operations are being performed in a single-threaded application. Which class would be appropriate to use for string manipulation, and why?
- String
- StringBuffer
- StringBuilder
- StringJoiner
In a single-threaded application with frequent string concatenation, StringBuilder is the most suitable choice. It's efficient because it doesn't create new objects when you modify the string, which can save memory and reduce overhead. StringBuffer is also thread-safe but slightly slower due to synchronization. String creates a new string each time you modify it, and StringJoiner is used for joining strings, not efficient for concatenation.
Which access modifier allows a member to be accessed from within its own class only?
- default (no modifier)
- private
- protected
- public
In Java, the private access modifier restricts access to the member to within the same class only. It is used to encapsulate the implementation details and hide them from external classes. The other options allow varying degrees of access to the member from outside the class.
Which interface or class should a class use or extend to create a new thread in Java?
- Executor
- Runnable
- Thread
- java.lang
In Java, to create a new thread, a class should implement the Runnable interface. The Runnable interface defines a single abstract method, run(), which should be overridden to provide the code that the new thread will execute. The other options are not used for directly creating a new thread.
What is the impact of using PrintWriter in file handling without automatic line flushing?
- It buffers data and may not immediately write it to the file.
- It ensures efficient memory usage and high-speed writing to the file.
- It has no impact on file handling.
- It throws an error if used without automatic line flushing.
PrintWriter in Java buffers data by default, which means it doesn't immediately write to the file. Without automatic line flushing, you must manually flush the buffer (using flush()), or it may not write data until the buffer is full or the program exits. This buffering can improve performance but may lead to unexpected behavior if you forget to flush.
Which of the following reference data types is used for storing a single character?
- Character
- Integer
- String
- char
The reference data type Character is used for storing a single character in Java. It is different from the primitive data type char, which also stores a single character but is not a reference data type. String is used to store sequences of characters, and Integer is for integer values.
Deadlocks involving synchronized methods or blocks can potentially be resolved by ________.
- using fewer threads
- using more synchronization
- using more threads
- using thread priority
Deadlocks occur when two or more threads are blocked, each waiting for a resource that the other holds. To resolve deadlocks involving synchronized methods or blocks, one approach is to use fewer threads or to minimize the usage of synchronized sections to reduce the chances of threads waiting indefinitely, thereby avoiding ________.
Can an interface contain static methods in Java?
- No
- Only if it doesn't have any abstract methods.
- Only if it doesn't have any default methods.
- Yes
Yes, Java allows interfaces to contain static methods, introduced in Java 8. Static methods in interfaces can be called without creating an instance of the interface and are often used for utility functions or factory methods.
Imagine developing a JavaFX application where UI responsiveness is critical. How might you ensure that long-running tasks (like database operations) do not freeze the UI?
- Disable the UI during long-running tasks and re-enable it after the task completes.
- Increase the JavaFX UI thread priority to give more resources to UI updates during long-running tasks.
- Use Java's Thread.sleep() method to pause the UI updates temporarily while the task runs.
- Use JavaFX Task and Platform.runLater() to run long tasks on background threads and update the UI on the JavaFX application thread.
In JavaFX, long-running tasks like database operations should be executed on background threads to avoid freezing the UI. The recommended approach is to use the Task class and Platform.runLater() to safely update the UI from background threads. The other options are not suitable for ensuring UI responsiveness during long tasks.