Java Interview Questions (8)

Java Interview Questions

9 Apr, 2007 No Comment

What are the types of messaging? - There are two kinds of Messaging. Synchronous messaging involves a client that waits for the server to respond to a message. Asynchronous messaging involves a client that does not wait for a message from the server. An event is used to trigger a message from a server.
What is publish/subscribe messaging? - With publish/subscribe message passing the sending application/client establishes a named topic in the JMS broker/server and publishes messages to this queue. The receiving clients register (specifically, subscribe) via the broker to messages by topic; every subscriber to a topic receives each message published to that topic. There is a one-to-many relationship between the publishing client and the subscribing clients.

9 Apr, 2007 No Comment

How do you call a Stored Procedure from JDBC? - The first step is to create a CallableStatement object. As with Statement and PreparedStatement objects, this is done with an open Connection object. A CallableStatement object contains a call to a stored procedure.
```
  CallableStatement cs =
    con.prepareCall("{call SHOW_SUPPLIERS}");
  ResultSet rs = cs.executeQuery();
```
Is the JDBC-ODBC Bridge multi-threaded? - No. The JDBC-ODBC Bridge does not support concurrent access from different threads. The JDBC-ODBC Bridge uses synchronized methods to serialize all of the calls that it makes to ODBC. Multi-threaded Java programs may use the Bridge, but they won’t get the advantages of multi-threading.

9 Apr, 2007 No Comment

How do you handle your own transaction ? - Connection Object has a method called setAutocommit(Boolean istrue)
- Default is true. Set the Parameter to false , and begin your transaction
What is the normal procedure followed by a java client to access the db.? - The database connection is created in 3 steps:
1. Find a proper database URL
2. Load the database driver
3. Ask the Java DriverManager class to open a connection to your database
In java code, the steps are realized in code as follows:

9 Apr, 2007 No Comment

What gives Java its “write once and run anywhere” nature? - Java is compiled to be a byte code which is the intermediate language between source code and machine code. This byte code is not platorm specific and hence can be fed to any platform. After being fed to the JVM, which is specific to a particular operating system, the code platform specific machine code is generated thus making java platform independent.
What are the four corner stones of OOP? - Abstraction, Encapsulation, Polymorphism and Inheritance.

9 Apr, 2007 No Comment

How many methods do u implement if implement the Serializable Interface? - The Serializable interface is just a “marker” interface, with no methods of its own to implement. Other ‘marker’ interfaces are
```
  java.rmi.Remote
  java.util.EventListener
```