The ______ method of the Animation class is used to play the animation in reverse order from the end position.
- playBackward()
- reverse()
- reverseOrder()
- rewind()
To play an animation in reverse order from the end position in JavaFX, you can use the reverse() method of the Animation class. This method reverses the animation, making it appear as if it's playing backward. The other options do not specifically address reversing animations.
To handle a transaction in JDBC, first, you must set the auto-commit mode to ________ before starting the transaction.
- FALSE
- TRUE
- commit
- rollback
In JDBC, to handle a transaction, you must set the auto-commit mode to false using the setAutoCommit(false) method before starting the transaction. This ensures that multiple SQL statements can be treated as a single transaction until explicitly committed. Setting it to true would mean auto-commit mode is enabled, where each SQL statement is treated as a separate transaction.
Imagine you are developing a system where multiple transactions are handled concurrently. How would you manage to prevent dirty reads and ensure data consistency?
- Encapsulating data access logic within stored procedures or functions to prevent direct access to data.
- Implementing database isolation levels like READ_COMMITTED or SERIALIZABLE to control the visibility of data changes to different transactions.
- Using synchronized methods in Java to lock the critical section of code to prevent concurrent access to the data.
- Utilizing database transactions and employing concepts like ACID (Atomicity, Consistency, Isolation, Durability) to ensure data integrity.
In a multi-transactional system, it's crucial to manage data consistency and prevent dirty reads. Database isolation levels help in achieving this. READ_COMMITTED ensures that a transaction can't read uncommitted changes from other transactions. SERIALIZABLE provides the highest level of isolation, preventing concurrent access to the same data. It's essential to understand these concepts for maintaining data integrity.
A constructor in Java cannot have a return type and is declared with the same name as the ________.
- class
- interface
- method
- object
In Java, constructors are special methods used to initialize objects. They have the same name as the class they belong to, making option 1 ("class") the correct choice. Constructors cannot have a return type.
The ______ arithmetic operator divides the left-hand operand by the right-hand operand and returns the remainder.
- %
- *
- +
- -
The "%" (modulo) operator in Java is used to divide the left-hand operand by the right-hand operand and returns the remainder. For example, "10 % 3" returns 1 because 10 divided by 3 leaves a remainder of 1. The other operators perform different arithmetic operations.
What is the initial capacity of the HashMap when no size is defined, and how is it related to the number of entries it can ideally accommodate without resizing?
- 16, and it can accommodate 16 entries.
- 10, and it can accommodate 10 entries.
- 32, and it can accommodate 32 entries.
- The initial capacity is not defined, and it dynamically adjusts as entries are added.
In Java, when you create a HashMap without specifying an initial capacity, it defaults to an initial capacity of 16. This means that initially, the HashMap can accommodate 16 key-value pairs. However, as the number of entries increases and reaches a certain threshold (usually 75% of the capacity), the HashMap automatically resizes itself, doubling its capacity. So, option (a) is correct, with the explanation that it can ideally accommodate 16 entries initially but will resize when necessary.
What will be the output of calling a method overridden in the child class?
- It depends on how the method is called
- It depends on the method's signature
- The child class's method will always be called
- The parent class's method will always be called
When a method is overridden in the child class, the version of the method in the child class is called when the method is invoked on an instance of the child class. This is known as method overriding and is a fundamental concept in object-oriented programming.
In a multithreaded application where multiple threads are reading and writing to a shared User object, how would you ensure that the read and write operations are thread-safe?
- Ensure that all threads run in a single thread by using a single-core CPU.
- Implement a ReadWriteLock to control access to the User object.
- Use synchronized methods for read and write operations on the User object.
- Use the volatile keyword for the User object.
To ensure thread safety in a multithreaded application, you can use synchronized methods for read and write operations on the shared User object. This prevents multiple threads from accessing and modifying the object simultaneously, avoiding data corruption and race conditions. The other options do not provide effective thread safety mechanisms.
The ______ method of the Lock interface is used to acquire the lock.
- acquire()
- lock()
- tryLock()
- unlock()
The lock() method of the Lock interface is used to acquire the lock. It blocks until the lock is available and then acquires it. The unlock() method is used to release the lock. The acquire() and tryLock() methods are not part of the standard Lock interface in Java.
Consider a scenario where you have a large number of short-lived asynchronous tasks. Which type of ExecutorService would you consider using and why?
- CachedThreadPoolExecutor: A thread pool that dynamically creates and recycles threads.
- FixedThreadPoolExecutor: A fixed-size thread pool with a specific number of threads.
- ScheduledThreadPoolExecutor: A thread pool for scheduling tasks at a fixed rate or delay.
- SingleThreadPoolExecutor: A single-threaded ExecutorService.
In this scenario, the CachedThreadPoolExecutor is suitable. It dynamically adjusts the number of threads based on the workload, making it efficient for short-lived tasks. SingleThreadPoolExecutor and FixedThreadPoolExecutor have limitations for such cases, and ScheduledThreadPoolExecutor is designed for scheduling tasks, not managing short-lived tasks.