How can you prematurely exit a loop in Java?
- break statement
- continue statement
- goto statement (not recommended)
- return statement
You can use the break statement to prematurely exit a loop in Java. When break is encountered within a loop, it immediately terminates the loop's execution, allowing you to exit the loop based on a certain condition or event. It is a commonly used control flow statement for loop termination.
You are working on a class that must not be instantiated and only serves to provide utility static methods. How would you utilize constructors to enforce this non-instantiability?
- Define a constructor with a boolean parameter to control instantiation.
- Define a private constructor to prevent instantiation and make the class final to prevent subclassing.
- Make the class abstract with a default constructor for utility methods.
- Utilize a public constructor with a warning message to discourage instantiation.
To enforce non-instantiability of a class meant for utility static methods, you should define a private constructor, preventing external instantiation. Additionally, making the class final ensures that it cannot be subclassed, further enforcing its intended usage as a utility class with only static methods.
Using the ________ method, you can run multiple SQL statements using a single Statement object, separated by semicolons.
- execute()
- executeBatch()
- executeQuery()
- executeUpdate()
The executeBatch() method in JDBC allows you to execute multiple SQL statements using a single Statement object, with statements separated by semicolons. This is particularly useful for batch processing. Other options are valid for executing single SQL statements.
Which exception might be thrown when establishing a connection to a URL in Java?
- ConnectionException
- IOException
- URLException
- URLIOException
When establishing a connection to a URL in Java, the IOException exception might be thrown. This can happen if there are issues with the network, the URL is invalid, or there are other I/O-related problems during the connection process. The other exception names are not standard in Java.
In a data processing application, you are looping through a large dataset and performing operations. Midway, an error occurs. How would you ensure that the loop gracefully handles errors and continues processing the remaining data?
- Use a break statement to exit the loop when an error occurs.
- Use a throw statement to re-throw the error and stop the loop immediately.
- Use a try-catch block to catch and handle exceptions.
- Use an if-else statement to check for errors and skip the current iteration if an error occurs.
To gracefully handle errors during data processing, you would use a try-catch block to catch exceptions, perform error handling, and continue processing the remaining data. The other options either don't handle errors properly or would terminate the loop.
In Java 12 and later versions, the ________ expression can be used as an alternative to the traditional switch statement, providing a more concise and readable format.
- for-each
- lambda
- switch
- ternary
In Java 12 and later, you can use the "lambda" expression as an alternative to the traditional switch statement. This feature is also known as "switch expressions." It provides a more concise and readable way to handle multiple cases within a single expression.
The writeObject method belongs to the ______ class.
- ObjectOutputStream
- ObjectSerializer
- ObjectWriter
- SerializationWriter
The writeObject method belongs to the ObjectOutputStream class in Java. This method allows you to customize the process of writing an object to an output stream during serialization. It's often used to handle special cases when serializing objects. The other options are not related to writing objects during serialization.
The showAndWait() method is used to display a ________ and wait for the user's response.
- Alert
- Dialog
- Notification
- Popup
In JavaFX, the Alert class is often used to display dialog boxes that require user interaction. The showAndWait() method is used to display an alert dialog and wait for the user's response before proceeding. The other options, Dialog, Popup, and Notification, are not the classes commonly associated with this method.
Which method is used to read a single character from a character input stream in Java?
- read()
- readChar()
- readCharacter()
- readLine()
The read() method in Java's character input stream classes is used to read a single character at a time. It returns an integer representing the Unicode code point of the character read. The other options are not valid methods for reading a single character from a character input stream.
Consider a scenario where you need to enforce singleton behavior on a class. How would constructors play a role in ensuring this?
- Constructors are used to create multiple instances, each with a unique ID.
- Constructors are used to enforce thread safety in the singleton pattern.
- Constructors ensure single instance creation by marking the constructor as private and providing a static method to retrieve the instance.
- Constructors play no role in enforcing singleton behavior.
In the singleton pattern, constructors play a crucial role in enforcing the creation of a single instance of a class. To achieve this, the constructor is marked as private to prevent external instantiation, and a static method is provided to retrieve the single instance. This ensures that only one instance of the class exists throughout the application's lifecycle.