The ________ interface of the JDBC API provides cursor support, which allows forward and backward navigation through the result set.
- Connection
- ResultSet
- ResultSetMetaData
- Statement
The ResultSet interface in the JDBC API provides cursor support, allowing you to navigate through the result set of a database query. You can move forward and backward, retrieve data, and perform various operations on the result set. The other options do not provide cursor support.
The ________ reference data type in Java is immutable and stores a sequence of characters.
- String
- StringBuilder
- List
- Array
The String class in Java is an immutable reference data type that stores a sequence of characters. Being immutable means that once a String object is created, its content cannot be changed. Understanding the immutability of strings is crucial for efficient string manipulation in Java.
In Java 8, the Stream API introduces the concept of stream processing, which is influenced by the ________ paradigm.
- functional
- imperative
- object-oriented
- procedural
The Stream API in Java 8 is influenced by the functional programming paradigm. Functional programming focuses on treating computation as the evaluation of mathematical functions, which aligns well with the stream processing concept in Java's Stream API.
What will be the result of attempting to compile and run a Java class that contains a variable declared as int public;?
- A compilation error will occur due to using a reserved keyword as a variable name.
- The code will compile and run without errors.
- The code will compile but result in a runtime error.
- The code will compile but will produce a warning message.
In Java, "public" is a reserved keyword used to declare access modifiers. Using it as a variable name will result in a compilation error since you cannot use reserved keywords as variable names. This is a fundamental rule in Java's syntax. Attempting to compile and run such code will indeed lead to a compilation error.
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.
Can a constructor return a value in Java?
- Yes, a constructor can return a value, which is the default value of the class's primary data type.
- No, constructors cannot return values in Java.
- A constructor can return values, but only if it has the same name as the class.
- A constructor can return values, but they must be of type 'void.'
b) is correct. Constructors in Java cannot return values, and their return type is always 'void.' a), c), and d) are incorrect statements.
The keyword ________ is used within a constructor to call another constructor in the same class.
- constructor()
- extend()
- super()
- this()
In Java, the this() keyword is used within a constructor to call another constructor in the same class. This is called constructor chaining and allows you to reuse code logic among constructors in a class. The super() keyword is used to call a constructor of the superclass. The other options are not valid for constructor invocation.
What is the key difference between the poll() and remove() methods when used with a Queue in Java?
- poll() returns null if the queue is empty, while remove() throws an exception.
- poll() removes and returns the head of the queue if it's not empty, while remove() removes and returns the head but throws an exception if the queue is empty.
- poll() removes and returns the head of the queue if it's not empty, while remove() returns null if the queue is empty.
- poll() and remove() have the same behavior when used with a Queue.
In Java, the poll() method is used to retrieve and remove the head of a queue. If the queue is empty, it returns null. On the other hand, the remove() method also removes the head of the queue but throws a NoSuchElementException if the queue is empty. So, option (b) is the correct answer, with the explanation that the key difference is in the handling of empty queues.