Java Programming

Java OOP, collections, multithreading

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Difficulty: All Easy Medium Hard 151–160 of 476

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.151 Medium JDBC

Which JDBC method executes UPDATE, INSERT, or DELETE statements?

A executeQuery()

B execute()

C executeUpdate()

D executeBatch()

Correct Answer: C. executeUpdate()

EXPLANATION

executeUpdate() executes DML statements and returns the number of rows affected.

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Q.152 Medium JDBC

What is the purpose of Connection.commit() in JDBC?

A Close the connection

B Save all changes made in the current transaction

C Rollback transactions

D Create a new statement

Correct Answer: B. Save all changes made in the current transaction

EXPLANATION

commit() saves all changes made during the current transaction permanently to the database.

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Q.153 Medium JDBC

In JDBC, what is the purpose of CallableStatement?

A To execute simple SELECT queries

B To execute stored procedures and functions

C To batch multiple SQL statements

D To manage transaction isolation levels

Correct Answer: B. To execute stored procedures and functions

EXPLANATION

CallableStatement is used to call stored procedures and stored functions in the database.

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Q.154 Medium JDBC

What is Connection pooling in JDBC and why is it used?

A A method to execute multiple SQL statements in parallel

B Reusing database connections to improve performance and reduce overhead

C A feature to automatically backup database connections

D A mechanism to encrypt database connections

Correct Answer: B. Reusing database connections to improve performance and reduce overhead

EXPLANATION

Connection pooling maintains a pool of reusable connections, reducing the cost of creating new connections repeatedly.

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Q.155 Medium JDBC

Which JDBC constant specifies read-only access for a ResultSet?

A ResultSet.CONCUR_READ_ONLY

B ResultSet.TYPE_READ_ONLY

C ResultSet.MODE_READ

D ResultSet.ACCESS_READ_ONLY

Correct Answer: A. ResultSet.CONCUR_READ_ONLY

EXPLANATION

CONCUR_READ_ONLY is the concurrency constant that specifies a read-only ResultSet.

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Q.156 Medium JDBC

In JDBC, what is the purpose of the ResultSetMetaData interface?

A To execute SQL queries

B To retrieve information about the structure of a ResultSet

C To manage database connections

D To handle transaction management

Correct Answer: B. To retrieve information about the structure of a ResultSet

EXPLANATION

ResultSetMetaData provides information about columns, data types, and column properties of a ResultSet.

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Q.157 Medium JDBC

What happens when Connection.setAutoCommit(false) is called in JDBC?

A Auto-commit is enabled immediately

B Manual transaction control is enabled; changes require explicit commit

C All pending transactions are rolled back

D The connection is closed automatically

Correct Answer: B. Manual transaction control is enabled; changes require explicit commit

EXPLANATION

Setting autoCommit to false enables manual transaction management where commit() must be explicitly called.

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Q.158 Medium JDBC

Which JDBC method is used to set an input parameter in a PreparedStatement?

A setParameter()

B setInt(), setString(), etc.

C bindParameter()

D addParameter()

Correct Answer: B. setInt(), setString(), etc.

EXPLANATION

PreparedStatement uses type-specific setter methods like setInt(), setString(), setDate() to bind parameters.

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Q.159 Medium JDBC

What is the difference between ResultSet.TYPE_SCROLL_INSENSITIVE and ResultSet.TYPE_SCROLL_SENSITIVE?

A Insensitive is faster; Sensitive allows concurrent updates visibility

B Insensitive allows backward navigation; Sensitive does not

C Sensitive is read-only; Insensitive allows modifications

D They are identical and can be used interchangeably

Correct Answer: A. Insensitive is faster; Sensitive allows concurrent updates visibility

EXPLANATION

TYPE_SCROLL_INSENSITIVE doesn't reflect concurrent database changes, while TYPE_SCROLL_SENSITIVE may reflect such changes.

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Q.160 Medium JDBC

In a JDBC batch operation, what does executeBatch() return?

A A ResultSet object

B An array of integers representing update counts

C A single integer value

D A boolean value

Correct Answer: B. An array of integers representing update counts

EXPLANATION

executeBatch() returns an int array where each element represents the number of rows affected by each statement in the batch.

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