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Java how to Override equals() and hashCode() method

2011-12-27T00:08:00.000+05:30

Object class has following five non final methods. 1. clone()2. equals(Object obj)3. finalize()4. hashCode()5. toString() Every Java class has Object as a superclass so by default all above methods are provided in every java class. In this article we will discuss in detail the concepts of equals() and hashCode() method. We will discuss why it is necessary to override these methods and how we can

Difference between DELETE, TRUNCATE and DROP command

2011-12-22T22:45:00.000+05:30

Most often asked interview question: What is difference between DELETE, TRUNCATE and DROP command? This article gives a detailed comparison between them. Points-of-parity DELETE TRUNCATE DROP What does command do? Delete some or all rows of a table. Delete all rows of a table. Removes a table from the database. The integrity constraints will

Handling Very Large Numbers in Java

2011-12-21T22:12:00.001+05:30

In Java, sometimes we need to handle integer numbers larger than Long.MAX_VALUE or floating-point values larger than Double.MAX_VALUE. Use the BigInteger or BigDecimal values available in package java.math to handle large values. Java Overflow In arithmetic operations when using int or long, if the value becomes too large, Java saves only the low order 32 bits for int and 64 bits for longs and

Create Simple Tooltips using JQuery and CSS

2011-12-14T23:07:00.000+05:30

In this post we had implemented simple Tooltips using JQquery and CSS. What is a Tooltip? Tooltip is a message appears when cursor is positioned over an image, icon, link or any other HTML element. Example 1: JQuery Tooltip showing Text Message In this example mouseover on text and it will show tooltip showing a text message. HTML CSS <style type="text/css"> .tooltip { margin: 8px;

Java Exception Handling Tutorial with Examples

2011-12-11T08:48:00.000+05:30

This post explains exception handling in java and suggests best practices for exception handling. An exception in Java is an object that is created when any abnormal, unexpected events or extraordinary conditions occur in program. Handling of those is exception handling in Java. This exception object has data that store information about nature of problem. This exception object is thrown and

How to write and run simple Java program - Helloworld Example

2011-12-10T21:21:00.000+05:30

This article is for Java beginners and will introduce you to Java programming language. In this post we will learn how to write, save, compile and run a simple java program using classic HelloWorld Example. NOTE: Before moving ahead I’m assuming that we have downloaded and installed the Java SE Development Kit on our machine. Also set required environment Variables for Java. For more details

Difference between String, StringBuffer and StringBuilder in Java

2011-12-07T08:36:00.000+05:30

String is most commonly used class in Java programming. Java also provides two other classes StringBuffer and StringBuilder. We need to carefully choose between these three depending on the requirement. Thus it is important to understand difference among them. Points of Difference 1. String class objects are immutable objects means that they can’t be altered. It always creates a new object

JDBC Interview Questions & Answers for Java Developers – Part 2

2011-12-03T22:47:00.000+05:30

This post is an extension to my previous post JDBC Interview Questions & Answers for Java Developers – Part 1. We have compiled few more JDBC questions. Read these interview questions. What's the difference between a primary key and a unique key? Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the

JDBC Interview Questions & Answers for Java Developers – Part 1

2011-12-03T21:18:00.001+05:30

We have compiled list of some popular JDBC questions for Java Developers. Read these interview questions. How many types of JDBC Drivers are present and what are they? JDBC drivers are divided into four types or levels. The different types of jdbc drivers are: Type 1: JDBC-ODBC Bridge driver (Bridge)Type 2: Native-API/partly Java driver (Native)Type 3: All Java/Net-protocol driver (

Run multiple instances of Apache Tomcat server on a single machine

2011-12-01T23:31:00.001+05:30

This post explains us how to run multiple instances of Apache Tomcat server on a single machine. We want to do this may be for load balancing, separating web application etc. We are assuming that no instructions needed to install first tomcat instance, you just need to install it by extracting tomcat zip file. Here we are going to install second tomcat assuming that we have done with the first

Example on how to use Google Chart API

2011-11-29T11:36:00.000+05:30

This post lists the steps and demonstrates a simple example on how to use Google Chart API for chart creation. Google Charts API gives us capability to create pretty graphs simply by using an URL with correct parameters specified. It is fairly flexible, with many things you can change and customize. The chart is interactive and displays information on mouse over. Here is the API link: http://

Getting and setting value of html elements using jquery

2011-11-27T16:09:00.000+05:30

This post explains how to get and set value of HTML elements using jquery. Though it can be used in different ways to select elements, we will stick to selecting elements by id for the purpose of this tutorial. An element can be accessed using its id as follows: $('#elementId') Textbox, Hidden field and Textarea All these elements share a common method. val() method is used to get and

Jquery text or banner rotator example

2011-11-26T15:40:00.001+05:30

In this post we had implemented a simple text or banner rotator example using jquery. This jquery displays multiple texts or banners one by one with a fading effect. Text Rotator Using Jquery HTML CSS <style type="text/css"> body { background-color: #BCDFDB; color: #025C7F; font-family: verdana, arial;}#quotes { margin: 0; padding: 100px;

Jquery to search text in HTML Table

2011-11-26T10:51:00.002+05:30

This jquery search for a text in HTML table and based on that it filter out rows that contains the text in any of its table cells. User Interface has HTML table and a search box above the table to type the search term. HTML Code <div><p> <label for="search"> <strong>Search Box</strong> </label> <input type="text" id="search" /></p><table width="40%" id="searchTable" border=

Spring MVC Exception Handling Tutorial

2011-11-24T23:44:00.002+05:30

This post explains ways to handle exceptions in Spring MVC. Exception handling is always recommended in application and all exceptions should be handled gracefully to show a valid message to end user in case of exception. In web.xml, you can map a custom error page to an exception: <error-page> <error-code>404</error-code> <location>/WEB-INF/pages/404.jsp</location> </

Spring Security login example using database

2011-11-20T17:24:00.000+05:30

This post explains how to use database to do the form-based login authentication in Spring Security 3. Technologies used: 1) Spring 3.0.5.RELEASE2) Spring Security 3.0.5.RELEASE3) Spring JDBC 3.0.5.RELEASE4) MySQL 5.15) JSTL 1.26) Eclipse (Indigo Release)7) JDK 1.68) Maven 3 NOTE: Spring Security 3.0 requires a Java 5.0 Runtime Environment or higher. My last post Spring Security 3 – Form Login

Spring + Quartz scheduler integration example

2011-11-17T23:27:00.001+05:30

This tutorial explains how to do task scheduling in Spring using Quartz scheduler framework. Spring actually integrates well with Quartz and works beautifully. 1. Make a Scheduler Task Make a normal java class and create a scheduler task in it. Below SchedulerTask.java has a method printCurrentTime() we want to schedule. This method print current time on console in every one minute. package

How to display user defined error messages in Spring Security

2011-11-16T23:04:00.000+05:30

In case of error, Spring Security displays predefined error messages. For Example when authentication is failed, following predefined error messages will be displayed : Spring display : Bad credentials Spring Security stored messages in “messages.properties” inside “spring-security-core.jar“, see below snapshot: This post explains how to override Spring's error messages and display your custom

Get current logged in user's username in Spring Security

2011-11-16T22:41:00.000+05:30

This post explains three ways to get current logged in user's username in Spring Security. 1. Using SecurityContextHolder + Authentication.getName() Inside the SecurityContextHolder we store details of the user currently interacting with the application. Spring Security uses an Authentication object to represent this information. You won't normally need to create an Authentication object

Spring Security 3 – Form Login and Logout Tutorial

2011-11-13T16:14:00.002+05:30

By default, Spring Security provides a login form if login form is not provided, Spring Security 3 – MVC integration Tutorial demonstrates this. In this post we will enhance this and show how to use custom login form and use it in Spring Security to authenticate user. Technologies used: 1) Spring 3.0.5.RELEASE2) Spring Security 3.0.5.RELEASE3) JSTL 1.24) Eclipse (Indigo Release)5) JDK 1.66)

Spring Security 3 – MVC integration Tutorial

2011-11-05T00:39:00.003+05:30

This post explains how to integrate Spring Security with minimal configuration in a simple Spring 3 MVC application. Spring security adds security feature to web application and it is highly customizable. We can also implement "user defined" security checks. Technologies used: 1) Spring 3.0.5.RELEASE2) Spring Security 3.0.5.RELEASE3) Eclipse (Indigo Release)4) JDK 1.65) Maven 3 NOTE: Spring

Spring 3 MVC Eclipse Project using Maven

2011-11-03T00:25:00.003+05:30

This post explains how to develop simple Spring 3 MVC Hello World Eclipse Project using Maven. Technologies used: 1) Spring 3.0.5.RELEASE2) JDK 1.63) Maven 34) Eclipse (Indigo Release) Steps to create Maven Project in Eclipse m2eclipse offers the ability to create a Maven project in Eclipse. Please make sure that Maven is configured in windows and m2eclipse is installed in Eclipse. If needed,

Setting Environment Variables JAVA_HOME, PATH and CLASSPATH in Java in Windows

2011-10-17T23:02:00.001+05:30

After Java installation our second step is to set environment variables PATH, CLASSPATH and JAVA_HOME for compiling and running of Java applications. Let's discuss them one by one. PATH (For Windows Users) When we launch any program from command line prompt, operating system use PATH environment variable to locate executable programs. In other words, PATH maintains a list of directories for

Steps to install Maven M2eclipse Core Components into Eclipse

2011-10-16T08:50:00.002+05:30

Installation of m2eclipse Core Components includes installing the entire core Wizards, the POM Editor, Maven Repository integration and Maven integration. m2eclipse Core Update Site: http://m2eclipse.sonatype.org/sites/m2e Below are the steps to install it (in my case I’m using Eclipse Indigo Release) 1) Open Eclipse and select Help > Install New Software. This will open Install dialog box. 2)

Apple unveils iPhone 4S; but no iPhone 5

2011-10-05T09:40:00.002+05:30

On October 4th, Apple unveils iPhone 4s defying expectations of people eagerly waiting for iPhone 5. iPhone 4s phone has no major design changes and looks exactly like old one. Apple insist that iPhone 4s is loaded with many new features. iPhone 5 is likely to come in late 2012 or early 2013. This phone is an upgraded version of iPhone 4. Apple with launch of this phone also launched IOS 5,