In a data processing application, if the data processing task fails, it needs to be retried a specified number of times. How can this be implemented using Future, Callable, and ExecutorService in Java?
- Implement a custom retry mechanism within the Callable task, where you catch exceptions, increment a retry counter, and resubmit the task if the retry limit is not reached.
- Use a separate thread to monitor the task's status and resubmit it if it fails, ensuring a specified number of retries.
- Use a try-catch block within the main method to catch exceptions and manually resubmit the task until the retry limit is reached.
- Use the ExecutorService's retryTask() method to specify the number of retries and the task to execute.
To implement data processing with retries, you can customize the Callable task to catch exceptions, increment a retry counter, and resubmit the task if the retry limit is not reached. This provides fine-grained control over retries using Future, Callable, and ExecutorService.
When a thread acquires a lock for a synchronized method, what happens to the other threads that are trying to access it?
- They are paused and put into a waiting state until the lock is released by the thread that acquired it.
- They are terminated abruptly.
- They continue to execute concurrently without any impact.
- They throw an exception immediately.
In Java, when a thread acquires a lock for a synchronized method, other threads that attempt to access the same synchronized method are paused and put into a waiting state. They will wait until the thread that acquired the lock releases it, allowing one thread to execute the synchronized method at a time.
The Timeline class in JavaFX uses instances of the ______ class to define the moment (sub-time) within relative to the cycle at which the key value is to be applied.
- KeyFrame
- TimeInstance
- TimeMarker
- TimePoint
In JavaFX, the KeyFrame class is used to define moments within a timeline where specific actions or animations should occur. It is often used with the Timeline class to specify when key values should be applied during an animation. The KeyFrame allows precise control over the timing of animations in JavaFX.
What is the key difference in approach between the Merge Sort and Quick Sort algorithms?
- Merge Sort is a comparison-based sorting algorithm that divides the array into smaller subarrays, sorts them, and then merges them back together.
- Merge Sort is an in-place sorting algorithm that rearranges elements within the original array.
- Quick Sort is a stable sorting algorithm that maintains the relative order of equal elements.
- Quick Sort uses a divide-and-conquer approach and selects a pivot element to partition the array into two subarrays.
The key difference in approach between Merge Sort and Quick Sort lies in how they divide and conquer. Merge Sort divides the array into smaller subarrays, sorts them, and then merges them back together. Quick Sort, on the other hand, selects a pivot element and partitions the array into two subarrays, which are then sorted independently. Merge Sort is not an in-place sorting algorithm, while Quick Sort typically is.
The statement that is used to create an exception object and hand it off to the runtime system is called ________.
- catch
- finally
- throw
- try
In Java, the throw statement is used to create an exception object and hand it off to the runtime system. This allows you to manually throw exceptions when specific conditions are met in your code.
What is the impact of using Lambda expressions on Java's Garbage Collection?
- Lambda-generated objects are never collected by Garbage Collection.
- Lambda-generated objects may lead to more frequent Garbage Collection.
- Lambdas are directly managed by Garbage Collection.
- Lambdas have no impact on Garbage Collection.
Lambda expressions in Java can generate additional objects, known as "captured variables" or "closure instances." These objects may lead to more frequent Garbage Collection, as they are subject to memory management. However, Java's Garbage Collection system is designed to efficiently handle short-lived objects, so the impact is often minimal. Understanding this impact is essential for optimizing memory usage in applications that heavily use Lambdas.
How many else if blocks can be used after an if block?
- As many as needed
- Maximum of three
- None
- Only one
You can use as many else if blocks as needed after an if block. The else if statement allows you to add additional conditions to check when the initial if condition is false. This flexibility enables you to handle various cases in your code, making it more versatile.
The primitive data type boolean in Java can have the values ________ or ________.
- Yes, No
- True, False
- 0, 1
- Positive, Negative
In Java, the boolean data type can only have two possible values: true or false. These values represent binary logic where true means "yes" or "on," and false means "no" or "off." It is essential to understand the fundamental concept of boolean data type for conditional expressions and logical operations in Java.
How does Java restrict a class from being used to create objects?
- By declaring it as an abstract class
- By marking its constructor as private
- By specifying it as a singleton class
- By using the final keyword
In Java, when you mark a class constructor as private, it prevents the class from being instantiated from outside the class, effectively restricting the creation of objects. Abstract classes can't be instantiated directly, but this is not the primary means of restriction. The final keyword prevents subclassing but doesn't restrict object creation. A singleton pattern controls object creation, but it's not the typical way to restrict a class.
Considering memory usage and performance, what is the impact of using += for string concatenation in a loop?
- += creates a new string object in each iteration, leading to high memory usage and poor performance.
- += is optimized by the Java compiler, resulting in low memory usage and good performance.
- += is suitable for small string concatenations but not recommended for large-scale operations.
- += is the same as using StringBuilder and is always the best choice for string concatenation.
Using += for string concatenation in a loop can have a significant impact on memory usage and performance. It creates a new string object in each iteration, leading to increased memory consumption and reduced performance, especially for large-scale operations. It is not optimized by the Java compiler, unlike using StringBuilder, which is more efficient for concatenating strings in a loop.