In the interface declaration 'interface Pair', how many type parameters does it have?

The correct answer is B: Two. The interface has two type parameters: K and V, making it a generic interface that can be implemented with different type combinations.

What happens if an exception is thrown inside a synchronized block?

The correct answer is A: The lock is automatically released when exiting the block. Java guarantees that the lock is released when exiting a synchronized block, whether normally or via an exception. This is why synchronized is considered safer than manual lock management.

In Java, which method of Throwable class is used to obtain the cause of an exception?

The correct answer is B: getCause(). The getCause() method returns the cause (underlying Throwable) of this Throwable. It's useful for exception chaining.

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().

A batch update operation fails partially. How can you identify which statements failed in the batch?

The correct answer is B: Use the int array returned by executeBatch() to check individual update counts. executeBatch() returns an int array where each element represents the update count for the corresponding statement. A value of -3 (Statement.EXECUTE_FAILED) indicates failure for that statement.

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Java Programming
JDBC

Java OOP, collections, multithreading

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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.1 Hard JDBC

In JDBC metadata operations, which method is used to retrieve information about table structure, column names, and their data types?

A getDatabaseMetaData()

B getMetaData() on ResultSet

C getColumnCount() and getColumnName()

D Both B and C together

Correct Answer: D. Both B and C together

EXPLANATION

getMetaData() on ResultSet returns ResultSetMetaData which provides column information. getColumnCount() and getColumnName() are methods of ResultSetMetaData used to retrieve structure details.

Test

Q.2 Hard JDBC

A Java application requires connection pooling to handle 1000+ concurrent database requests efficiently. Which JDBC component should be implemented?

A Direct DriverManager.getConnection() calls

B DataSource interface with connection pool implementation like HikariCP or C3P0

C Creating new Connection for each request manually

D Using Statement caching only

Correct Answer: B. DataSource interface with connection pool implementation like HikariCP or C3P0

EXPLANATION

DataSource with connection pooling frameworks (HikariCP, C3P0) efficiently manages connections by reusing them, reducing overhead. Direct getConnection() calls create new connections each time, which is inefficient for high concurrency.

Test

Q.3 Medium JDBC

In JDBC 2024-25, which exception is thrown when attempting to use a closed Connection object?

A SQLException

B SQLClientInfoException

C SQLInvalidAuthorizationSpecException

D SQLNonTransientConnectionException

Correct Answer: A. SQLException

EXPLANATION

A SQLException (specifically a SQLNonTransientConnectionException as a subclass) is thrown when operations are attempted on a closed Connection. SQLException is the general exception for database access errors.

Test

Q.4 Medium JDBC

When using ResultSet in JDBC, which cursor type allows bidirectional movement through rows but does not reflect database changes?

A TYPE_FORWARD_ONLY

B TYPE_SCROLL_INSENSITIVE

C TYPE_SCROLL_SENSITIVE

D TYPE_DYNAMIC

Correct Answer: B. TYPE_SCROLL_INSENSITIVE

EXPLANATION

TYPE_SCROLL_INSENSITIVE allows movement in both directions (previous, next, absolute) but doesn't reflect changes made to the database after the ResultSet was created. TYPE_SCROLL_SENSITIVE would reflect changes.

Test

Q.5 Medium JDBC

A developer needs to execute the same SQL query multiple times with different parameters. Which JDBC feature should be used to optimize performance?

A Statement with loop execution

B PreparedStatement with parameterized queries

C CallableStatement for all queries

D Multiple Connection objects

Correct Answer: B. PreparedStatement with parameterized queries

EXPLANATION

PreparedStatement pre-compiles the query and allows parameter binding, reducing overhead and improving performance for repeated executions. It also prevents SQL injection.

Test

Q.6 Easy JDBC

In a JDBC application, which interface is responsible for executing SQL queries and returning ResultSet objects?

A Statement

B Connection

C Driver

D DataSource

Correct Answer: A. Statement

EXPLANATION

The Statement interface is used to execute SQL queries. Connection creates the statement, Driver manages connections, and DataSource provides connection pooling, but Statement is the actual executor.

Test

Q.7 Hard JDBC

In a JDBC application using batch updates, what happens if one statement in the batch fails?

A All statements are executed, and failure is reported

B All statements are rolled back automatically

C Only failed statement is skipped

D Behavior depends on database configuration

Correct Answer: D. Behavior depends on database configuration

EXPLANATION

executeBatch() behavior on failure varies by database and driver. BatchUpdateException is thrown, containing update counts for each statement. Explicit transaction control is recommended.

Test

Q.8 Medium JDBC

Which JDBC feature allows monitoring of database metadata like table structure and column information?

A DatabaseMetaData interface

B ResultSetMetaData interface

C ParameterMetaData interface

D StatementMetaData interface

Correct Answer: A. DatabaseMetaData interface

EXPLANATION

DatabaseMetaData (obtained from Connection.getMetaData()) provides information about the entire database like tables, columns, keys, and supported features.

Test

Q.9 Hard JDBC

A query execution takes 5 seconds consistently. Which JDBC optimization technique should NOT be used for this scenario?

A Connection pooling

B Batch processing for multiple inserts

C Using indexes on frequently queried columns

D Increasing setFetchSize() value

Correct Answer: D. Increasing setFetchSize() value

EXPLANATION

If query execution itself is slow (5 seconds), the bottleneck is in database operations, not data transfer. Increasing setFetchSize() only optimizes data retrieval, not query execution.

Test

Q.10 Medium JDBC

What is the correct way to handle resource management in JDBC with Java 7+?

A try-catch-finally blocks with explicit close()

B try-with-resources statement (try-with parentheses)

C Using finally blocks only

D Automatic garbage collection handles it

Correct Answer: B. try-with-resources statement (try-with parentheses)

EXPLANATION

try-with-resources automatically closes AutoCloseable resources (Connection, Statement, ResultSet), preventing connection leaks elegantly.

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