What exception is thrown when a file is not found while creating FileInputStream?

The correct answer is B: FileNotFoundException. FileNotFoundException (a subclass of IOException) is thrown when the specified file does not exist or cannot be opened.

Which of the following is NOT a character stream class in Java?

The correct answer is C: FileInputStream. FileInputStream is a byte stream class, not a character stream. FileReader, BufferedWriter, and PrintWriter are all character stream classes.

Which collection class is thread-safe without explicit synchronization?

The correct answer is C: ConcurrentHashMap. ConcurrentHashMap uses segment-based locking (in older versions) or fine-grained locking to provide thread-safety without synchronizing the entire map. Other options require external synchronization or Collections.synchronizedMap().

Which of the following will throw a NullPointerException? String s = null; System.out.println(s.length());

The correct answer is C: s.length(). Calling a method on a null reference throws NullPointerException. s.length() tries to invoke method on null, causing the exception.

Which of the following access modifiers allows a variable to be accessed only within the same class?

The correct answer is A: private. The 'private' access modifier restricts access to only within the same class. It provides the highest level of encapsulation.

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Java Programming

Java OOP, collections, multithreading

212 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 61–70 of 212

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.61 Hard JDBC

When using JDBC with Spring Framework in 2024-25, which approach is recommended for resource management?

A Manual try-catch blocks

B Try-with-resources statement

C JdbcTemplate with Spring

D DriverManager only

Correct Answer: C. JdbcTemplate with Spring

EXPLANATION

JdbcTemplate in Spring Framework automatically manages JDBC resources and is the recommended approach in modern applications.

Test

Q.62 Hard JDBC

In JDBC, what is the significance of setting FetchSize on a Statement when dealing with large ResultSets?

A It determines the maximum number of rows to fetch from database in one round-trip

B It sets the total memory allocated for ResultSet

C It automatically closes the ResultSet

D It enables caching of all rows in memory

Correct Answer: A. It determines the maximum number of rows to fetch from database in one round-trip

EXPLANATION

FetchSize controls how many rows are fetched from the database at once, optimizing performance for large datasets.

Test

Q.63 Hard JDBC

Which JDBC feature should be used for executing multiple SQL statements in a batch for optimal performance?

A executeUpdate() in a loop

B executeBatch() with addBatch()

C execute() method

D Multiple Statement objects

Correct Answer: B. executeBatch() with addBatch()

EXPLANATION

executeBatch() with addBatch() reduces network round-trips and improves performance for bulk operations.

Test

Q.64 Hard JDBC

In a JDBC application, when using transactions with setAutoCommit(false), what happens to intermediate savepoints if rollback() is called?

A All changes are saved

B Only savepoint changes are rolled back

C All changes since last commit are rolled back

D The entire connection is closed

Correct Answer: C. All changes since last commit are rolled back

EXPLANATION

When rollback() is called without savepoints, all changes made since the last commit are undone and rolled back.

Test

Q.65 Hard JDBC

Consider a scenario: A developer uses Statement with user input directly in SQL queries. What is the primary risk?

A Slower query execution

B SQL Injection attacks

C Memory leaks

D Connection timeout

Correct Answer: B. SQL Injection attacks

EXPLANATION

Direct concatenation of user input in SQL queries exposes the application to SQL injection attacks. PreparedStatement should be used instead.

Test

Q.66 Hard JDBC

In a multi-threaded JDBC application, why should each thread have its own Connection object?

A To improve database performance

B Connections are not thread-safe and sharing causes race conditions

C To reduce memory usage

D It is just a best practice with no technical requirement

Correct Answer: B. Connections are not thread-safe and sharing causes race conditions

EXPLANATION

JDBC Connections are not thread-safe. Each thread must have its own Connection to prevent concurrent access issues and data corruption.

Test

Q.67 Hard JDBC

What is the optimal approach to handle JDBC resources to prevent memory leaks in a production application?

A Use try-catch blocks and manually close resources

B Rely on garbage collection to close resources

C Use try-with-resources statement to auto-close resources

D Create resources globally and close them at application shutdown

Correct Answer: C. Use try-with-resources statement to auto-close resources

EXPLANATION

Try-with-resources (try-with-resources statement) automatically closes AutoCloseable resources, preventing memory leaks.

Test

Q.68 Hard JDBC

Consider a scenario where a developer retrieves a ResultSet and then closes the Statement object. What happens to the ResultSet?

A The ResultSet remains valid and can still be accessed

B The ResultSet becomes invalid in most drivers (implementation-dependent)

C An immediate SQLException is thrown

D The database automatically commits pending changes

Correct Answer: B. The ResultSet becomes invalid in most drivers (implementation-dependent)

EXPLANATION

Closing a Statement typically invalidates its associated ResultSet in most JDBC drivers, though behavior may vary.

Test

Q.69 Hard JDBC

A developer creates a JDBC connection but forgets to close it. What might be the consequence?

A Automatic garbage collection will close it immediately

B Resource leak leading to exhaustion of database connections

C The program will automatically rollback all transactions

D No impact as JDBC handles it automatically

Correct Answer: B. Resource leak leading to exhaustion of database connections

EXPLANATION

Unclosed connections remain allocated, eventually exhausting the connection pool and causing application failures.

Test

Q.70 Hard JDBC

In JDBC, what is the purpose of using a SavePoint in a transaction?

A To save the current connection state

B To create a checkpoint within a transaction that can be rolled back to independently

C To automatically commit pending changes

D To lock the database for exclusive access

Correct Answer: B. To create a checkpoint within a transaction that can be rolled back to independently

EXPLANATION

A SavePoint allows you to roll back part of a transaction without rolling back the entire transaction. You can create nested transactions by setting multiple savepoints and rolling back to specific ones.

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