Java Interview Questions and Answers Set 10

91.What are Directives ?

Directives are instructions that are processed by the JSP engine, when the page is compiled to a servlet. Directives are used to set page-level instructions, insert data from external files, and specify custom tag libraries. Directives are defined between < %@ and % >.The different types of directives are shown below:

Include directive: it is used to include a file and merges the content of the file with the current page.

Page directive: it is used to define specific attributes in the JSP page, like error page and buffer.

Taglib: it is used to declare a custom tag library which is used in the page.

92.What is the difference between HashSet and HashMap?

HashSet contains only values whereas HashMap contains entry(key,value). HashSet can be iterated but HashMap need to convert into Set to be iterated.

93.What is the difference between HashSet and HashMap?

HashSet contains only values whereas HashMap contains entry(key,value). HashSet can be iterated but HashMap need to convert into Set to be iterated.

94.What are Scriptlets ?

In Java Server Pages (JSP) technology, a scriptlet is a piece of Java-code embedded in a JSP page. The scriptlet is everything inside the tags. Between these tags, a user can add any valid scriplet.

95.What are Decalarations ?

Declarations are similar to variable declarations in Java. Declarations are used to declare variables for subsequent use in expressions or scriptlets. To add a declaration, you must use the sequences to enclose your declarations.

96.What are Expressions ?

A JSP expression is used to insert the value of a scripting language expression, converted into a string, into the data stream returned to the client, by the web server. Expressions are defined between <% = and %> tags.

97.Explain the role of Driver in JDBC.

The JDBC Driver provides vendor-specific implementations of the abstract classes provided by the JDBC API. Each driver must provide implementations for the following classes of the java.sql package:Connection, Statement, PreparedStatement, CallableStatement, ResultSet and Driver.

98.What is the purpose Class.forName method ?

This method is used to method is used to load the driver that will establish a connection to the database.

99.What is the advantage of PreparedStatement over Statement ?

 PreparedStatements are precompiled and thus, their performance is much better. Also, PreparedStatement objects can be reused with different input values to their queries.

100.What is the use of CallableStatement ?

Name the method, which is used to prepare a CallableStatement. A CallableStatement is used to execute stored procedures. Stored procedures are stored and offered by a database. Stored procedures may take input values from the user and may return a result. The usage of stored procedures is highly encouraged, because it offers security and modularity.The method that prepares a CallableStatement is the following:

CallableStament.prepareCall();