How can you read data from a URL using Java?
- Use the InputStream class
- Use the Scanner class
- Use the URLConnection class
- Use the readData() method
To read data from a URL in Java, you typically use the URLConnection class to open a connection to the URL and then use the InputStream class to read the data. The other options are not standard methods for reading data from a URL.
Which operator can be used to invert the sign of a numeric expression?
- !
- +
- -
- ~
The - (minus) operator can be used to invert the sign of a numeric expression. For example, if you have a variable int x = 5;, then -x would give you -5. The other options are not used for inverting the sign of numeric values.
Which of the following is a valid method to execute a stored procedure using JDBC?
- CallableStatement.execute() with a procedure
- executeQuery() with a stored procedure call
- executeStoredProc()
- executeUpdate() with a stored procedure call
To execute a stored procedure using JDBC, you typically use the CallableStatement interface and its execute() method with a procedure call. The other options (executeStoredProc(), executeQuery() with a stored procedure call, and executeUpdate() with a stored procedure call) are not standard methods for executing stored procedures in JDBC.
You need to perform different actions on each element of a heterogeneous list (i.e., containing different types of objects). How would you implement the loop to handle different types and perform type-specific actions?
- Use a custom iterator with type-specific handlers.
- Use a for-each loop with instanceof checks.
- Use a series of if statements to check each element's type.
- Use a switch statement inside a for loop.
To handle different types in a heterogeneous list, you can use a for-each loop and check each element's type using the instanceof operator. This approach allows you to perform type-specific actions. The other options may not be as flexible or efficient for this task.
Imagine you are developing a multi-threaded application for a bank. How would you ensure that when multiple threads are trying to update the same account, the account data remains consistent?
- Employing optimistic locking techniques such as versioning, where each thread checks a version number before updating the account.
- Implementing thread-safe data structures like ConcurrentHashMap to store account information.
- Using synchronized methods or blocks to lock access to the account data when it's being updated.
- Utilizing atomic operations provided by classes like AtomicInteger to ensure atomic updates of account data.
In a multi-threaded bank application, consistency can be achieved by using synchronized methods or blocks to ensure that only one thread can access and update the account data at a time. This prevents race conditions and data corruption. Other options, like using thread-safe data structures or atomic operations, can help with performance but may not guarantee consistency in complex scenarios. Optimistic locking with versioning can also be used to handle concurrent updates.
Which of the following classes is used to create a button in JavaFX?
- Button
- CheckBox
- Label
- TextField
In JavaFX, the Button class is used to create a button. Buttons are interactive elements in a graphical user interface, and you can use the Button class to create them and add event handlers. The other classes mentioned are used for different purposes.
To specify a repeating behavior in an animation, ______ method is used in JavaFX.
- cycleAnimation()
- repeatAnimation()
- setCycleCount()
- setRepeatCount()
In JavaFX, the setCycleCount() method is used to specify the number of times an animation should repeat. By setting the cycle count to a specific value, you can control how many times the animation should loop or repeat, creating repeating behaviors in your animations.
Which of the following classes is mainly used to establish a connection to the database in JDBC?
- java.sql.Connection
- java.sql.DriverManager
- java.sql.ResultSet
- java.sql.Statement
The java.sql.DriverManager class in JDBC is primarily used for establishing database connections. It provides methods like getConnection to create connections to a database server. The other classes mentioned (Connection, Statement, and ResultSet) are used after the connection is established for various database operations.
How can transactions be managed in JDBC to ensure data integrity?
- By using Connection.setAutoCommit(false) and manually committing transactions using Connection.commit()
- By using Connection.setAutoCommit(true) and allowing transactions to automatically commit on every SQL statement execution
- By using Connection.setReadOnly(true) to prevent any data modification, thus ensuring data integrity
- By using Connection.setTransactionIsolation() to set the desired isolation level, ensuring data consistency
In JDBC, transactions can be managed by setting auto-commit to false using Connection.setAutoCommit(false). This allows you to manually commit transactions using Connection.commit(). This approach ensures data integrity by allowing you to group multiple SQL statements into a single transaction and ensuring that they are either all executed or none at all. Setting auto-commit to true (option 2) will not provide the same level of control over transactions. Options 3 and 4 are unrelated to managing transactions in this context.
What is the output of the following code snippet: System.out.println(!(4 > 3) && (7 > 8));?
- Compilation Error
- FALSE
- Runtime Error
- TRUE
The expression !(4 > 3) && (7 > 8) is evaluated as false && false, which results in false. The ! operator negates the result of the first comparison, and && requires both operands to be true for the whole expression to be true. So, the output is false.