What is the role of Savepoint in JDBC transactions?
- It allows you to create a named point within a transaction where you can roll back to later
- It is a way to commit a transaction and make the changes permanent
- It is used to save the current state of a database before making any changes
- It is used to terminate a transaction prematurely
Savepoints in JDBC transactions allow you to create a named point within a transaction. This named point can be used to roll back the transaction to that specific point if needed, providing finer-grained control over transaction rollback. Options 2, 3, and 4 do not accurately describe the role of Savepoint in JDBC transactions.
Which of the following statements correctly creates an object of a class named 'Dog'?
- Dog dog = new Dog();
- Dog obj = createObject();
- Dog.create();
- Dog.new();
To create an object of a class named 'Dog' in Java, you should use the class name followed by the constructor using the new keyword, like this: Dog dog = new Dog();. The other options are not the correct way to create an object of a class in Java.
To write a newline character when using FileWriter, you can use ________.
- "n"
- "n"
- "r"
- 'n'
To write a newline character when using FileWriter, you can use "n". This escape sequence represents a newline character in Java and is commonly used to create line breaks in text files.
Imagine you are working on a system that categorizes user feedback into positive, negative, and neutral based on certain keywords. Describe how you'd structure your control statements to efficiently categorize the feedback.
- Create a custom machine learning model
- Implement a decision tree algorithm
- Use if-else statements with keyword checks
- Utilize regular expressions for keyword matching
To efficiently categorize user feedback based on keywords, you can use if-else statements. For each feedback, check if it contains specific positive, negative, or neutral keywords. Regular expressions can also be helpful for more complex matching. While decision trees and machine learning models are powerful for sentiment analysis, they might be overkill for simple keyword-based categorization.
Which of the following access modifiers is allowed for a method in an interface?
- default
- private
- protected
- public
In Java interfaces, all methods are implicitly public, whether you declare them as such or not. You cannot use the private, protected, or default access modifiers for methods in an interface.
Which class allows multiple threads to work in parallel but blocks them until all threads are finished?
- CountDownLatch
- CyclicBarrier
- Semaphore
- ThreadGroup
The CyclicBarrier class allows multiple threads to work in parallel but blocks them until all threads have reached a certain point (barrier) in the code. Once all threads have reached the barrier, they can continue executing. It is commonly used for tasks that can be divided into subtasks that need to be completed before the main task can proceed.
Is it possible to extend a class defined as final?
- No, you cannot extend a class that is declared as final.
- Yes, you can extend a final class.
- You can extend a final class only in the same package.
- You can extend a final class, but it requires special annotations.
In Java, a class declared as "final" cannot be extended. The "final" keyword indicates that the class cannot be subclassed. Attempting to extend a final class will result in a compile-time error. This feature is often used when you want to prevent further modification or extension of a class, such as in utility classes or classes that are critical to the design.
Which method is used to retrieve the protocol type of a URL in Java?
- fetchProtocol()
- getProtocol()
- getURLProtocol()
- retrieveProtocol()
In Java, to retrieve the protocol type of a URL, you should use the getProtocol() method of the URL class. It returns a String containing the protocol, such as "http," "https," "ftp," etc. The other options do not exist as valid methods for this purpose.
Can we overload the "+" operator to concatenate two strings and add two integers in a custom class?
- No, Java does not support operator overloading.
- Yes, by defining a method named + in the custom class.
- Yes, by defining methods named add and concatenate for the custom class.
- Yes, by using the + operator with different parameter types in the method definition.
No, Java does not support operator overloading. In Java, the + operator is not overloaded for user-defined classes. The + operator is only used for addition when applied to numeric data types and for string concatenation when used with strings. Therefore, you cannot define custom behavior for the + operator in user-defined classes.
Does Java support operator overloading?
- No, not at all.
- Only for arithmetic ops.
- Yes, for all operators.
- Yes, for selected ops.
Java does not support operator overloading for custom classes. While some languages do allow operator overloading, Java enforces a fixed set of operators for built-in types, and you cannot create custom operator overloads. This limitation helps maintain code readability and prevents ambiguity.