In Java, what is JDBC and what problem does it solve in database programming?

Introduction / Context:
JDBC (Java Database Connectivity) is a core technology for Java developers who interact with relational databases. Interviewers frequently ask what JDBC is to ensure that you understand how Java applications talk to databases in a vendor independent way. Without JDBC or similar APIs, each database would require its own custom protocol and client code, making applications difficult to port and maintain.

Given Data / Assumptions:

• We are working with relational databases such as MySQL, PostgreSQL, or Oracle.
• Our Java application needs to send SQL queries and updates to these databases.
• Different vendors offer different drivers, but we want a standard API.
• We want to handle connections, statements, and result sets in a consistent manner.

Concept / Approach:
JDBC is a Java API defined in the java.sql and javax.sql packages. It provides interfaces and classes for establishing database connections, executing SQL statements, and processing the results. JDBC acts as a bridge between Java code and the underlying database driver. Application code uses standard JDBC interfaces, and database vendors supply JDBC drivers that implement those interfaces for their specific products, allowing the same Java code to work with different databases with minimal changes.

Step-by-Step Solution:
1. The application loads a JDBC driver, either automatically via the service mechanism or explicitly using Class.forName(). 2. It obtains a Connection object, typically by calling DriverManager.getConnection(url, user, password), which represents a session with the database. 3. It creates a Statement or PreparedStatement object to send SQL commands such as SELECT, INSERT, UPDATE, or DELETE. 4. For queries, it executes the statement and receives a ResultSet, which allows iteration over rows and access to column values by name or index. 5. After finishing database operations, the application closes the ResultSet, Statement, and Connection to release resources.

Verification / Alternative check:
You can verify the role of JDBC by writing a simple program that connects to a local database, executes a small query, and prints the results. Changing the database vendor usually requires changing only the connection URL and driver dependency, while the core JDBC code remains almost the same, confirming that JDBC provides vendor independence.

Why Other Options Are Wrong:
Option B is incorrect because Java source code is stored in .java files, not in any JDBC format. Option C is wrong because compilation from .java to .class is handled by the javac compiler, not by JDBC. Option D is unrelated; user interface design uses libraries such as Swing, JavaFX, or web frameworks, not JDBC.

Common Pitfalls:
Common issues when using JDBC include forgetting to close resources, which can lead to connection leaks, and constructing SQL strings by concatenation, which can cause SQL injection vulnerabilities. Using PreparedStatement with parameters and try with resources helps mitigate these problems. Also, as applications grow, it is common to move from plain JDBC to higher level frameworks like JPA or Spring JDBC, but a solid understanding of JDBC remains valuable.

Final Answer:
JDBC is a Java API that provides a standard way to connect to relational databases, execute SQL statements, and process results.