In Java, when a subclass has the same method as declared in the parent class, it is known as method ________.
- hiding
- inheriting
- overloading
- overriding
When a subclass has the same method name, return type, and parameters as declared in the parent class, it is known as method overriding. The subclass provides a specific implementation for that method.
Consider a scenario where two threads are trying to access synchronized methods in a single class instance. Describe how the synchronized methods will manage the access of these two threads.
- Both threads can execute the synchronized methods concurrently, as synchronization allows multiple threads to access synchronized methods simultaneously.
- The first thread will execute the synchronized method, and the second thread will wait until the first thread completes its execution.
- The second thread will execute the synchronized method and then the first thread, as the order of execution is undefined.
- The second thread will execute the synchronized method if it has a higher priority than the first thread.
Synchronized methods in a single class instance are mutually exclusive. Only one thread can execute a synchronized method at a time. The first thread to enter the synchronized method will execute it, and the second thread will wait until the first one completes its execution. The order of execution is not defined, and thread priority does not affect synchronization.
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.
The ________ class represents a Uniform Resource Identifier and is designed to handle the complete URI syntax.
- URI
- URL
- URN
- UniformResource
The correct answer is "URI." In Java, the URI class is used to represent a Uniform Resource Identifier. It's designed to handle the complete URI syntax, including components like scheme, authority, path, query, and fragment. A URI is a broader concept that includes URLs (Uniform Resource Locators) and URNs (Uniform Resource Names).
The ________ method of the ExecutorService interface is commonly used to submit a Callable task and returns a Future object.
- execute
- invokeAll
- start
- submit
In Java, the submit method of the ExecutorService interface is used to submit a Callable task and returns a Future object representing the result of the computation. This method is commonly used for asynchronous tasks that return results.
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.