Imagine you are developing a multi-threaded application where threads are performing both read and write operations on shared resources. How would you ensure that the data is not corrupted without degrading performance significantly?
- Avoid synchronization altogether and use atomic operations.
- Implement read-write locks to allow multiple readers or a single writer.
- Use a single global lock for all shared resources.
- Use fine-grained locks for individual data elements.
In a multi-threaded application with both read and write operations on shared resources, using read-write locks is an effective approach. Read operations can occur concurrently, while write operations are exclusive. Fine-grained locks might lead to excessive contention and performance degradation. Using a single global lock can lead to contention, while avoiding synchronization altogether can risk data corruption.
In a web server application where numerous HTTP requests are processed, how would you utilize ExecutorService to efficiently manage resources and handle requests?
- Use a CachedThreadPoolExecutor: Dynamically adjust the thread pool size based on request load.
- Use a FixedThreadPoolExecutor: Allocate a fixed number of threads to handle incoming requests efficiently.
- Use a ScheduledThreadPoolExecutor: Schedule periodic tasks to manage resources.
- Use a SingleThreadPoolExecutor: Process requests sequentially to ensure thread safety.
In a web server application, a FixedThreadPoolExecutor is a good choice. It allocates a fixed number of threads, ensuring resource control and efficient handling of requests. CachedThreadPoolExecutor might create too many threads, SingleThreadPoolExecutor processes sequentially, and ScheduledThreadPoolExecutor is not designed for this purpose.
Which keyword is used in Java to test a condition?
- check
- if
- test
- verify
In Java, the if keyword is used to test a condition. It allows you to execute a block of code only if the condition specified inside the parentheses evaluates to true. The if statement is fundamental for implementing conditional logic in Java programs.
What is the purpose of the finally block in Java exception handling?
- To always execute code
- To catch exceptions
- To handle checked exceptions
- To throw exceptions
The finally block in Java exception handling is used to ensure that a certain block of code is executed regardless of whether an exception is thrown or not. It is typically used to perform cleanup actions, such as closing resources.
Which method can be used to temporarily pause the execution of a thread for a specified time?
- pause()
- sleep()
- stop()
- yield()
The sleep() method in Java is used to temporarily pause the execution of a thread for a specified amount of time. It's a way to introduce delays in a program and is often used for synchronization or timing purposes. The other options are not used for pausing threads in this manner.
The @FunctionalInterface annotation is used to indicate that an interface is to be used with ________.
- Annotations
- Generics
- Lambdas
- Threads
The @FunctionalInterface annotation is used to indicate that an interface is intended to be used with lambda expressions. It serves as a marker for functional interfaces, making it clear that they are designed to be used in lambda expressions.
Envision a situation where thread safety is a priority in your application. How can Lambda expressions be designed to minimize synchronization issues or shared mutability?
- By avoiding Lambda expressions altogether and relying on traditional synchronized methods for thread safety.
- By using Lambda expressions within synchronized blocks to ensure that critical sections of code are protected against concurrent access.
- By using nested Lambda expressions that share mutable variables across threads.
- By using volatile variables and Lock objects within Lambda expressions to manage thread safety.
Lambda expressions can be designed to promote thread safety by using synchronized blocks or other synchronization mechanisms within the Lambda body. This ensures that critical sections of code are protected from concurrent access, reducing synchronization issues and potential race conditions. It's crucial to be cautious when using shared mutable variables within Lambda expressions to avoid thread safety problems.
How would you handle a situation where a task submitted to ExecutorService is stuck or running for too long?
- There is no way to handle a stuck task in Java; it must be manually terminated by killing the JVM process.
- You can cancel the task using the cancel method of the Future object returned when submitting the task.
- You can increase the task timeout setting to give it more time to complete.
- You can use the ExecutorService.shutdownNow() method to forcefully terminate all running tasks and shut down the service.
When a task is stuck or running for too long, you can handle it by canceling the task using the cancel method of the Future object returned when submitting the task. This allows graceful termination of the task without affecting the entire application. Other options, like forcefully shutting down the ExecutorService or modifying the task's timeout settings, may have unintended consequences.
________ is an interface in JDBC, which can be used to move a cursor in the result set in both directions.
- PreparedStatement
- ResultSet
- ResultSetMetaData
- Statement
The ResultSet interface in JDBC is used to retrieve data from a database query result. It allows you to move a cursor in the result set in both directions, forward and backward, and retrieve data from the current row. This is especially useful when you need to navigate and process the result set efficiently.
Which index of a multi-dimensional array represents the row index in Java?
- First index
- It depends on the array's dimensions.
- Second index
- Third index
In Java, for a multi-dimensional array, the first index represents the row index. For a 2D array, it represents the row number, and for a 3D array, it represents the depth along the first dimension. The other indices represent the columns (2nd index), and if applicable, additional dimensions.