Synchronized methods prevent thread interference and memory consistency errors by allowing ________ thread(s) to execute the method's entire body.
- all but one
- multiple
- no additional thread(s)
- only one
Synchronized methods in Java allow only one thread to execute the method's entire body at a time. This ensures that there is no concurrent execution, preventing thread interference and memory consistency errors. Other threads are blocked until the executing thread completes the synchronized method. This is a fundamental concept in Java for ensuring thread safety.
What issues might arise if methods modifying static variables are not synchronized?
- Deadlocks may occur.
- Inconsistent or incorrect values can be assigned to static variables.
- No issues will arise.
- Only one thread can access static variables.
If methods modifying static variables are not synchronized, it can result in inconsistent or incorrect values being assigned to those variables. Since multiple threads can access and modify static variables concurrently, without synchronization, they may read and write to the variable at the same time, leading to data corruption or inconsistent state. Proper synchronization is essential to ensure thread safety when working with shared static variables.
Consider a multi-threaded environment, how can a loop potentially cause a race condition?
- The loop uses a single shared variable among multiple threads without proper synchronization, causing unpredictable results.
- The loop has a long execution time, increasing the likelihood of context switches and thread interference.
- The loop uses thread-local variables, eliminating the possibility of race conditions.
- The loop uses a synchronized keyword, ensuring thread safety.
In a multi-threaded environment, a race condition can occur when multiple threads access and modify a shared variable concurrently without proper synchronization. Option 1 correctly identifies this scenario. Option 2 refers to context switching but not directly to race conditions. Option 3 is a preventative measure, and Option 4 is a solution to race conditions, not a cause.
Which method is used to submit a task for execution to the ExecutorService and returns a Future object?
- addTaskToExecutor(Runnable task)
- execute(Runnable task)
- startTask(Callable
task) - submit(Runnable task)
The submit(Runnable task) method of the ExecutorService interface is used to submit a task for execution and returns a Future object. This Future can be used to monitor the progress and retrieve the result of the task asynchronously. The other options are not correct methods for submitting tasks to an ExecutorService.
A class in Java can contain _______, which are used to describe the properties of objects.
- Constructors
- Interfaces
- Methods
- Variables
In Java, a class can contain variables, which are used to describe the properties or attributes of objects. Methods are used to define the behaviors of objects. Constructors initialize objects, and interfaces declare methods that must be implemented.
The class ________ is used to create a text field in JavaFX.
- JText
- Text
- TextField
- TextInputField
In JavaFX, the TextField class is used to create a single-line text input field. It allows users to enter text or data. The other options, Text, TextInputField, and JText, are not the correct classes for creating text fields in JavaFX.
Which method of the String class is used to compare two strings for equality, ignoring case differences?
- compareTo()
- compareToIgnoreCase()
- equals()
- equalsIgnoreCase()
In Java, the equalsIgnoreCase() method of the String class is used to compare two strings for equality while ignoring differences in case. It returns true if the two strings are equal, regardless of whether the characters are in uppercase or lowercase. The other options, equals(), compareToIgnoreCase(), and compareTo(), do not perform case-insensitive comparisons.
What does the getConnection method of DriverManager class do?
- Closes an existing connection.
- Establishes a connection to a database.
- Executes a SQL query.
- Retrieves the JDBC driver's info.
The getConnection method of the java.sql.DriverManager class is used to establish a connection to a database. It takes parameters like the database URL, username, and password to create a connection to the specified database server. It does not close connections, retrieve driver info, or execute SQL queries.
Consider building a microservice handling requests from various clients and other microservices. How would you implement socket programming for non-blocking, asynchronous I/O and high throughput?
- Use Java's AsynchronousSocketChannel with NIO for asynchronous I/O and high throughput.
- Implement a multi-threaded server using Java's ServerSocket with one thread per connection.
- Employ Java's Socket with multi-threading for parallel request processing.
- Use Java's DatagramSocket with UDP for low overhead and high throughput.
To achieve non-blocking, asynchronous I/O, and high throughput in a microservice, Java's AsynchronousSocketChannel with NIO (Option 1) is the ideal choice. It allows for efficient handling of multiple connections without the need for a thread per connection, leading to scalability. Options 2 and 3, which use multi-threading, may lead to higher resource consumption and less scalability. Option 4, utilizing UDP with DatagramSocket, may not guarantee reliable, ordered, and synchronous communication, which is essential for a microservice handling requests.
Consider a scenario where a superclass method that throws an exception is overridden in the subclass. How should the exception handling be approached in this case, ensuring that the application's robustness is maintained?
- The subclass should rethrow the exception using throw to propagate it upward.
- The subclass should catch and handle the exception, ensuring that it doesn't break the application.
- The subclass should ignore the exception and not include any exception handling code.
- The subclass should modify the method signature to remove the exception declaration.
In this scenario, when a subclass overrides a superclass method that throws an exception, it should generally follow option 1. This means rethrowing the exception using throw to propagate it upward in the call stack. This approach maintains robustness by allowing higher-level code to handle the exception appropriately. Options 2 and 3 may lead to suppressed exceptions and unexpected behavior. Option 4 is incorrect as it doesn't handle the exception.