The ________ method of the Thread class is used to determine if a thread is still running.
- isActive()
- isAlive()
- isRunning()
- isThreadRunning()
The isAlive() method of the Thread class is used to check if a thread is still running. It returns true if the thread is alive, which means it has not completed execution yet.
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.
The deleteCharAt method is available in the ________ class to remove a character at a specified position.
- ArrayList
- Character
- String
- StringBuilder
The deleteCharAt method is available in the StringBuilder class in Java. It allows you to remove a character at a specified position within the StringBuilder object. The other classes mentioned do not have this method for character removal.
What value is stored at arr[1][2] after executing the following code snippet: int[][] arr = {{1,2,3}, {4,5,6}, {7,8,9}};?
- 3
- 6
- 8
- 9
The given code initializes a 2D array arr. arr[1] represents the second row (index 1), and arr[1][2] represents the third element in that row, which is 8. So, 8 is stored at arr[1][2].
The reduce() method in Java 8’s Stream API is used to ________.
- Combine elements into a single value
- Create a stream
- Perform filtering operations
- Transform elements
The reduce() method in Java 8's Stream API is used to combine elements into a single value. It can be used to perform tasks like summing up all elements, finding the maximum or minimum, or even concatenating strings in a stream. It's a fundamental operation for aggregating data.
In a scenario where order of the elements based on their insertion order is important, you might opt to use ________.
- HashMap
- HashSet
- LinkedHashMap
- TreeMap
In Java, if you want to maintain the order of elements based on their insertion order, you should opt for a LinkedHashMap. It combines the features of a hash table and a linked list to achieve this. A HashMap doesn't guarantee order, a TreeMap orders elements based on their natural order, and a HashSet doesn't guarantee any specific order.