Skip to main content

Java J2EE Interview Questions and Answers - Part 5

  1. Which containers use a Border layout as their default layout?- Window, Frame and Dialog classes use a BorderLayout as their layout.
  2. Which containers use a Flow layout as their default layout?- Panel and Applet classes use the FlowLayout as their default layout.
  3. What are wrapper classes?- Wrapper classes are classes that allow primitive types to be accessed as objects.
  1. What are Vector, Hashtable, LinkedList and Enumeration?- Vector : The Vector class provides the capability to implement a growable array of objects. Hashtable : The Hashtable class implements a Hashtable data structure. A Hashtable indexes and stores objects in a dictionary using hash codes as the object’s keys. Hash codes are integer values that identify objects. LinkedList: Removing or inserting elements in the middle of an array can be done using LinkedList. A LinkedList stores each object in a separate link whereas an array stores object references in consecutive locations. Enumeration: An object that implements the Enumeration interface generates a series of elements, one at a time. It has two methods, namely hasMoreElements() and nextElement(). HasMoreElemnts() tests if this enumeration has more elements and nextElement method returns successive elements of the series.
  2. What is the difference between set and list?- Set stores elements in an unordered way but does not contain duplicate elements, whereas list stores elements in an ordered way but may contain duplicate elements.
  3. What is a stream and what are the types of Streams and classes of the Streams?- A Stream is an abstraction that either produces or consumes information. There are two types of Streams and they are: Byte Streams: Provide a convenient means for handling input and output of bytes. Character Streams: Provide a convenient means for handling input & output of characters. Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream. Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.
  1. What is the difference between Reader/Writer and InputStream/Output Stream?- The Reader/Writer class is character-oriented and the InputStream/OutputStream class is byte-oriented.
  2. What is an I/O filter?- An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.
  3. What is serialization and deserialization?- Serialization is the process of writing the state of an object to a byte stream. Deserialization is the process of restoring these objects.
  1. What is JDBC?- JDBC is a set of Java API for executing SQL statements. This API consists of a set of classes and interfaces to enable programs to write pure Java Database applications.
  2. What are drivers available?- a) JDBC-ODBC Bridge driver b) Native API Partly-Java driver c) JDBC-Net Pure Java driver d) Native-Protocol Pure Java driver
  3. What is the difference between JDBC and ODBC?- a) OBDC is for Microsoft and JDBC is for Java applications. b) ODBC can’t be directly used with Java because it uses a C interface. c) ODBC makes use of pointers which have been removed totally from Java. d) ODBC mixes simple and advanced features together and has complex options for simple queries. But JDBC is designed to keep things simple while allowing advanced capabilities when required. e) ODBC requires manual installation of the ODBC driver manager and driver on all client machines. JDBC drivers are written in Java and JDBC code is automatically installable, secure, and portable on all platforms. f) JDBC API is a natural Java interface and is built on ODBC. JDBC retains some of the basic features of ODBC.
  1. What are the types of JDBC Driver Models and explain them?- There are two types of JDBC Driver Models and they are: a) Two tier model and b) Three tier model Two tier model: In this model, Java applications interact directly with the database. A JDBC driver is required to communicate with the particular database management system that is being accessed. SQL statements are sent to the database and the results are given to user. This model is referred to as client/server configuration where user is the client and the machine that has the database is called as the server. Three tier model: A middle tier is introduced in this model. The functions of this model are: a) Collection of SQL statements from the client and handing it over to the database, b) Receiving results from database to the client and c) Maintaining control over accessing and updating of the above.
  2. What are the steps involved for making a connection with a database or how do you connect to a database? a) Loading the driver : To load the driver, Class. forName() method is used. Class. forName(”sun. jdbc. odbc. JdbcOdbcDriver”); When the driver is loaded, it registers itself with the java. sql. DriverManager class as an available database driver. b) Making a connection with database: To open a connection to a given database, DriverManager. getConnection() method is used. Connection con = DriverManager. getConnection (”jdbc:odbc:somedb”, “user”, “password”); c) Executing SQL statements : To execute a SQL query, java. sql. statements class is used. createStatement() method of Connection to obtain a new Statement object. Statement stmt = con. createStatement(); A query that returns data can be executed using the executeQuery() method of Statement. This method executes the statement and returns a java. sql. ResultSet that encapsulates the retrieved data: ResultSet rs = stmt. executeQuery(”SELECT * FROM some table”); d) Process the results : ResultSet returns one row at a time. Next() method of ResultSet object can be called to move to the next row. The getString() and getObject() methods are used for retrieving column values: while(rs. next()) { String event = rs. getString(”event”); Object count = (Integer) rs. getObject(”count”);
  3. What type of driver did you use in project?- JDBC- ODBC Bridge driver (is a driver that uses native(C language) libraries and makes calls to an existing ODBC driver to access a database engine).

Comments

Post a Comment

Popular Posts

DOT NET Interview Questions with Answers

When not to use Design Patterns?Do not use design patterns in any of the following situations.• When the software being designed would not change with time.• When the requirements of the source code of the application are unique.If any of the above applies in the current software design, there is no need to apply design patterns in the current design and increase unnecessary complexity in the design.When to use Design Patterns?Design Patterns are particularly useful in one of the following scenarios.• When the software application would change in due course of time.• When the application contains source code that involves object creation and event notification.Benefits of Design Patterns:The following are some of the major advantages of using Design Patterns in software development.• Flexibility• Adaptability to change• ReusabilityWhat are Design Patterns?A Design Pattern essentially consists of a problem in a software design and a solution to the same. In Design Patterns each pattern…

Use Address bar effectively - Easy address bar commands

You are already familiar with quite a few browser address bar shortcuts. For instance, type some text in the address bar of your browser (e.g. apple), press Ctrl + Enter and the browser will automatically send you to the corresponding .com website (in this case, www.apple.com) Or type in some complex search query (e.g., site:firefox.com internet explorer) in the address bar, hit go and the browser will show results from your default search engine*. The address bar of Google Chrome is even smarter as it can offer live suggestions while you are typing the search query.
Other than these built-in shortcuts, you may also want to know about a couple of URL hacks (a better term would be "address bar commands") that let you do stuff from the address bar itself  – they are pretty easy to remember and don't require you to install any bookmarklets or add-ons (so you can use them on any computer and even some mobile phones).

1. Download videos from Youtube with URL Change easily – If …

Free Softwares , freewares : 16 July 09

Recover Files

Recover Files can undelete/recover deleted files. Its features
include: recovers files after deletion in the Recycle Bin, files
deleted from a network share, DOS command prompt, Shift+Delete is
used, when Move or Cut command are used, from Hard drives, floppy
disks, external USB disk / flash drivers, deleted by other
applications or by viruses, and much more; Supports FAT16, FAT32, NTFS
and NTFS 5 file systems; Performs non-destructive and read-only scan
and file recovery; Restores original create and modified file dates;
Supports unicode and non-alphabet languages; Filters files by name,
extension, folder and file type.

The 1.16 MB Recover Files, version 3.10 (July 06, 20079) for Windows
Vista, Windows 2003, Windows XP, Windows 2000, Windows 95, 98, ME and
Windows NT 4 can be downloaded at http://www.UndeleteUnerase.com/download.html

Exl-Plan Free

Exl-Plan Free is an Excel-based business finance planner, can be used
either for immediate or later projections, by both s…

MobileComm Recruits Freshers

Freshers IT Job Opening at MobilecommExperience: 0 - 1 Years 

Location: Delhi/NCR

Education: 
UG - B.Tech/B.E. - Computers, Electrical, Electronics/Telecomunication, Instrumentation   
PG - Post Graduation Not Required 

Industry Type: Telcom/ISP

Functional Area:
IT-Support, Telecom, Hardware

Job Description: 


*GSM Fundamentals. *RF Planning & Optimization. *Transmission Planning & Optimization. *3G Technologies
Desired Candidate Profile

B.E./B.Tech E&C, Telecommunication, Computers, IT 0 to 1 Yrs. experience Willing to work in GSM Mobile Industry Willing to travel anywhere in India Willing to undergo Job Oriented Training on self support basis
Company Profile
MobileComm Technologies (India) Pvt. Ltd. is subsidiary of MobileComm Professionals, Inc. USA - MobileComm Professionals Inc. is an engineering services organization supporting telecom cellular operators and OEM's to design, deploy and manage wireless networks. MobileComm is ISO9001 certified organization offering comp…

PDFzen: Simple document sharing.

PDFzen

You don't need to create an account to use PDFzen. Just upload your document and start editing. When you are finished, you can download the document as a PDF or get the link to share via email or social media. HTML5 PDF editing means PDFzen works right from the browser of your iPhone or iPad.

Features

Share
Easily share your document in many different ways.

Sign or Draw
Sign or draw anywhere on a document with the draw tool.

Type
Use the type tool to type on any part of a document.

Highlight
Point out important areas.

File Formats
.pdf, .doc, .docx, .xls, .xlx, .odt, .rtf)

Mobile-friendly
View and edit your PDFs on your PC, your phone, or your tablet.

Need to scan to PDF?
Use deskPDF Reader to scan your documents into PDF format, fill out forms, and easily share them with PDFzen integration.

Wallet_friendly

PDFzen will always be free to mark up, share and collaborate on documents. No strings attached, aver the developers

Check it out at https://pdfzen.c…

IBM Weekend Hiring for Java Professionals - 24th Nov 2012

Urgent Hiring Requirements for Java Professionals

Dear IBMer,

We solicit your help in bringing your friends and family members who qualify to apply for the given positions only.
We need your help & support to close the below positions. Please refer us good profiles like yours only & help us in closing the requirement.

Requirements Summary:

Please adhere to the demand:--

Skill -Java/J2EE with Spring/Hibernate/Struts
Exp Range - 3 to 4 yrs only (Please do not refer above 4yrs and below 3yrs as we will not be able to call them for the interview)
Joining Location - Pune/Kolkata/Chennai/Hyderabad

Interview Location - Bangalore/Chennai/Kolkata
Interview Date - 24th Nov 2012 (Only)


Important Note:Please refer to the above demand and share the profiles only for them to get the Interview Process started Immediately.Looking forward to your support to help us close these demand through Employee Referral only.16 years of Education is mandatory.Please check with the candidates that whether they have …

Contact Form

Name

Email *

Message *