1. What is executeQuery(String query)?

Statement executeQuery(String query) is used to execute Select queries and returns the ResultSet. ResultSet returned is never null even if there are no records matching the query. When executing select queries we should use executeQuery method so that if someone tries to execute insert/update statement it will throw java.sql.SQLException with message “executeQuery method can not be used for update”.

2. Do you know what is JSON? Can you represent JSON as Java Object?

JSON stands for Javascript object notation and is used to initialize Javascript objects. Yes it can be used as Java object also. Provide more info here

3. Tell me how do you differentiate between Core Java and Enterprise Java?

Core Java is something that provides the API's like regular expression, String handling, collections. But enterprise java involves writing scalable, secure and per-formant applications which can have large user base.

4. Explain me what do you mean by batch processing in JDBC?

Batch processing helps you to group related SQL statements into a batch and execute them instead of executing a single query. By using batch processing technique in JDBC, you can execute multiple queries which makes the performance faster.

5. Tell us how to disable caching on back button of the browser?

response.setHeader (“Expires”, “0”); //prevents caching at the proxy server

6. Explain me what is the purpose of JDBC ResultSet interface?

The ResultSet object represents a row of a table. It can be used to change the cursor pointer and get the information from the database.

7. What is public StackTraceElement[] getStackTrace()?

This method returns an array containing each element on the stack trace. The element at index 0 represents the top of the call stack whereas the last element in the array represents the method at the bottom of the call stack.

8. Explain me what is JDBC Connection interface?

The Connection interface maintains a session with the database. It can be used for transaction management. It provides factory methods that returns the instance of Statement, PreparedStatement, CallableStatement and DatabaseMetaData.

9. Tell us what is a finally block? Is there a case when finally will not execute?

Finally block is a block which always executes a set of statements. It is always associated with a try block regardless of any exception that occurs or not.
Yes, finally will not be executed if the program exits either by calling System.exit() or by causing a fatal error that causes the process to abort.

10. Do you know what is the difference between frameworks like Jquery/DOJO and AJAX?

Jquery and DOJO are java script frameworks for writing rich web applications but AJAX is a server communication mechanism which can issue requests without page reload.

Download Interview PDF