What will happen if two constructors in a class have the same parameter list in Java?
- It will cause a compilation error because Java does not allow duplicate constructors.
- The first constructor encountered will be used, and the second one will be ignored.
- It will lead to a runtime exception.
- It is not possible to have two constructors with the same parameter list in Java.
In Java, constructors are differentiated based on the number and type of parameters they accept. If two constructors in a class have the same parameter list, it will cause a compilation error because Java does not allow duplicate constructors. Option 2 is not correct; Java does not ignore constructors based on their order. Option 3 is inaccurate, as it would not lead to a runtime exception. Option 4 is also incorrect, as Java does not allow constructors with the same parameter list.
What is the purpose of a parameterized constructor in Java?
- It initializes class-level variables with default values.
- It allows the creation of multiple instances of the same class.
- It accepts one or more arguments to initialize instance variables.
- It is used to create static objects.
In Java, a parameterized constructor is used to initialize instance variables with values provided as arguments during object creation. This allows objects to be created with different initial states. Option 1 is incorrect as the default constructor initializes class-level variables, not parameterized constructors. Options 2 and 4 are not accurate descriptions of parameterized constructors.
How would you modify a for-each loop to run in parallel and utilize multiple cores/threads in Java?
- Convert the for-each loop into a traditional for loop and manually distribute loop iterations among threads using a thread pool.
- Use the Java Stream API and parallelStream() method on the collection to enable parallel execution of the for-each loop.
- Implement a custom parallelForEach() method that splits the loop iterations among threads using low-level concurrency constructs.
- Java automatically parallelizes for-each loops; no modification is required.
To run a for-each loop in parallel and utilize multiple cores/threads in Java, you can use the Java Stream API and the parallelStream() method on the collection. Option 2 correctly describes this approach. Option 1 involves manual thread management, Option 3 suggests creating a custom method, and Option 4 is not entirely accurate; Java does not automatically parallelize for-each loops.
In what scenarios would a for loop be less suitable compared to a while loop, especially concerning iterator-based operations?
- When you have a known number of iterations and need to iterate over elements in a collection.
- When the loop termination condition is based on a complex set of criteria that cannot be easily expressed in a for loop's initialization and condition.
- When you want to improve code readability and avoid common programming errors.
- When you want to ensure optimal performance and minimize memory usage.
A for loop is suitable when you have a known number of iterations, but a while loop is more appropriate when the loop termination condition depends on complex criteria that may not be easily expressed in a for loop's initialization and condition. Option 2 correctly identifies this scenario. Option 1 is not entirely accurate as for loops can also iterate over collections. Options 3 and 4 do not directly relate to the suitability of for loops compared to while loops.
Consider a scenario where you want to invert the sign of a numeric value only if a particular boolean condition is true. How can unary operators be utilized to achieve this without using an if statement?
- int invertedValue = (condition) ? -numericValue : numericValue;
- int invertedValue = (condition) ? numericValue : -numericValue;
- int invertedValue = -numericValue;
- int invertedValue = numericValue;
You can use the conditional (ternary) operator ? : to achieve this. If the condition is true, it negates the numericValue by using the unary minus operator. If false, it leaves the numericValue unchanged. Option 1 demonstrates this technique.
How can you securely serialize and deserialize objects to protect sensitive information during the process?
- Define custom serialization and deserialization logic with encryption and authentication mechanisms
- Employ access modifiers such as private and protected for fields and methods
- Ensure that classes are marked as final to prevent inheritance
- Use encryption techniques
To securely serialize and deserialize objects to protect sensitive information, you should use encryption techniques. Encrypting the data before serialization and decrypting it after deserialization ensures that the data remains confidential. While access modifiers and marking classes as final provide some level of security, they don't directly address the need for encryption. Custom logic with encryption and authentication is a comprehensive approach to security.
A ________ is a result-bearing computation that can be canceled and can compute the result asynchronously provided by ExecutorService.
- Callable
- ExecutorService
- Runnable
- Thread
A Callable in Java is a result-bearing computation that can be canceled and can compute the result asynchronously. It is typically used with ExecutorService to perform tasks that return values or throw exceptions.
What is the impact of using a SocketChannel in non-blocking mode over traditional blocking I/O socket communication?
- a. SocketChannel offers better performance with lower CPU usage.
- b. Non-blocking SocketChannel can handle only one connection at a time.
- c. Blocking I/O sockets are more suitable for high-throughput applications.
- d. Non-blocking SocketChannel improves data integrity.
Using SocketChannel in non-blocking mode (option a) can lead to improved performance with lower CPU usage compared to traditional blocking I/O sockets. Non-blocking SocketChannels can handle multiple connections concurrently. Option c is incorrect because non-blocking SocketChannels are often favored for high-throughput scenarios. Option d is not accurate as data integrity is not directly related to blocking or non-blocking mode.
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.