SQL INTERVIEW QUESTIONS AND ANSWERS

Accessing Data with JPA with memory-based h2 database

 

What You need

Java and OOP concepts (if not you can see my videos on java)

A favorite text editor or IDE : Intellj , Eclipse, VS code

Java 8 or later

Gradle 7.5+ or Maven 3.5+

Postman

 

Overview:

In this tutorial  will walk you through the process of building Springboot application that uses Spring Data JPA to store and retrieve data using in memory h2 relation database. Spring Data JPA make it easier to integrated data access technologies i.e. relational and non-relational databases, map-reduce frameworks, and cloud-based data services through java code.

 

Features

• Powerful repository and custom object-mapping abstractions

• Dynamic query derivation from repository method names

• Implementation domain base classes providing basic properties

• Support for transparent auditing (created, last changed)

• Possibility to integrate custom repository code

• Easy Spring integration via JavaConfig and custom XML namespaces

• Advanced integration with Spring MVC controllers

• Experimental support for cross-store persistence

 

Architecture:

Draw a diagram

 

How to  Accessing Data with JPA with New project or existing project?

1. navigate to https://start.spring.io to create a project.

2. Choose either Gradle or Maven and the language you want to use and language as java.

3. Click Dependencies and select Spring Data JPA and then H2 Database.

4. Click Generate. This will download a your project as Zip file.

5. Extract the project created in you desired folder.

6. Open the project in your favorite IDE

7. Create an Entity Class Customer and add desired fields with JPA annotation

8. Create CustomerRepository that extends CurdRepository which will provide the ability to perform CRUD operation into database.

9. Add findByLastName, findById custom methods to fetch records based on lastName and id

10. Create a CustomerController class that will accepts request from client to create, read, update and delete records.

11.  Run the application

12. Using Postman send request to server and verify its working as expected

 

Summary

Congratulations! You have written a simple application that uses Spring Data JPA to save objects to and fetch them from a database, all without writing a concrete repository implementation.

 

 

How to format code block in blogger? [Blogger Code Formatter]

 

 

1. Open the code formatter from the link http://codeformatter.blogspot.com/ 
2. Paste your source code block on the text area 
3. Customized the source code formatter option. (Default options worked for me )
4. Click format source code button
5. Copy paste the code and switch to html view in your blogger post and paste the html copied  to your blogger.

 Image Reference

 

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Install json-server to Mock your data with zero coding

 Install JSON Server

npm install -g json-server

if there is any issue with permission on Mac/Linux
sudo npm install -g json-server


Create a db.json file with some data

{
  "posts": [
    { "id": 1, "title": "json-server", "author": "typicode" }
  ],
  "comments": [
    { "id": 1, "body": "some comment", "postId": 1 }
  ],
  "profile": { "name": "typicode" }
}
Start JSON Server
json-server --watch db.json
Now if you go to http://localhost:3000/posts/1, you'll get

{ "id": 1, "title": "json-server", "author": "typicode" }

Resource: https://www.npmjs.com/package/json-server

Getting Started with Postgres Docker image

This command will download and run docker container

 sudo docker run --name dipen-postgres -p 5432:5432  -e POSTGRES_PASSWORD=<your-password> -d postgres  

Note: username = postgres


To run the image and expose the port 5442 of docker image to host port

 sudo docker run -p 5432:5432 postgres   

If you need to download postgresql client

 sudo apt-get install postgresql-client  

To connect the postgres data hosted in docker container with psql client

 psql -h localhost -p 5432 -U postgres  

https://docs.docker.com/samples/library/postgres/

https://zaiste.net/posts/docker_postgresql_how_to/


https://hub.docker.com/_/postgres/

https://docs.docker.com/engine/examples/postgresql_service/#connecting-from-your-host-system

Run Program in background Linux

To run the process in background use & at the end of bash command

 ./idea.sh &  

To view the jobs running in background

 jobs  

Useful links

Create React App

Install npm package manager before proceeding forward. Click Here

Step: 1 Creating react app npm package manager

 sudo npm install -g create-react-app  

  create-react-app my-app   

Navigate into my-app directory

 cd my-app  

Start your application

 npm start  

Now your application is served and you will be able to see output on your browser

 http://localhost:3000/  

Note :
If you run into error specified below

 ERROR: npm 5 is not supported yet  

Then you need to install 4.6.1 version globally with following command and follow the step one again.

 sudo npm i -g npm@4.6.1  

Useful links 
A re-introduction to JavaScript 
Reactjs

Install Nodejs and NPM Ubuntu 17

Step 1: Run the command to install LTS Release version.

 sudo apt-get install python-software-properties  

curl -sL https://deb.nodesource.com/setup_9.x | sudo -E bash -  

sudo apt-get install -y nodejs

Then verify your npm and nodejs installation.

 node -v   
 npm -v  

Useful link
  Nodejs

Share your docker image

Before Moving forward you have to define your container with Dockerfile. If you haven't done that follow the link Define your container with Dockerfile

Now it time to share your image across multiple platform and team using a docker registries. A registry is a collection of repositories, and a repository is a collection of images—sort of like a GitHub repository, except the code is already built.

Step 1: Make account on cloud.docker.com
Docker’s public registry is free and pre-configured, but there are many public ones to choose from.
Note that the docker CLI uses Docker’s public registry by default.

Login using docker CLI

 docker login  

After your are logged in successfully

Step 2: Tag the Image
Tagging image is good way of associating a local image with a repository on a registry.
For e.g. my-repo:my-first-image this puts the image in the my-repo repository and tag it as my-first-image.

 docker tag image username/repository:tag  

 docker tag my-app lamadipen/my-repo:first  

View list of images

 docker image ls  

Step 3: Publish your  image

  sudo docker push lamadipen/my-repo:first  

Now you can find your image on Docker Hub
Docker hub screen shot

Step 4: Pull the image and run image from the remote repository any where you want.

 docker run -p 4000:80 username/repository:tag  

For example

 docker run -p 4000:80 username/repository:tag  

This command pull your image from the repository if image isn't available on local machine and run it on your .

Step 5: Check your container serving you application
You will get response from your application on the browser if you check the link in your browser.

 http://localhost:8000/  

Define your container with Dockerfile

If you haven't installed Docker, then install it on your machine using the link (Installing Docker on Ubuntu).

Define a container with Dockerfile

Now its time to create your own custom environment using DockerFile. DockerFile behaves exactly the same wherever it runs enabling you to establish same standard configuration on dev, test and production environment.

Step 1: Create a folder (in my case i have created my-docker-img folder)
Step 2: Create a Dockerfile inside the folder (I have created Dockerfile.txt)
Dockerfile.txt

 # Use an official Python runtime as a parent image  
 FROM python:2.7-slim  
 # Set the working directory to /app  
 WORKDIR /app  
 # Copy the current directory contents into the container at /app  
 ADD . /app  
 # Set proxy server, replace host:port with values for your servers (If your are behind proxy server)  
 #ENV http_proxy host:port  
 #ENV https_proxy host:port  
 # Install any needed packages specified in requirements.txt  
 RUN pip install --trusted-host pypi.python.org -r requirements.txt  
 # Make port 80 available to the world outside this container  
 EXPOSE 80  
 # Define environment variable  
 ENV NAME World  
 # Run app.py when the container launches  
 CMD ["python", "app.py"]  

Step 3: Create app.py and requirement.txt specified in Docker file in the same folder.
app.py file is your python application that you want to deploy

app.py

 from flask import Flask  
 from redis import Redis, RedisError  
 import os  
 import socket  
 # Connect to Redis  
 redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)  
 app = Flask(__name__)  
 @app.route("/")  
 def hello():  
   try:  
     visits = redis.incr("counter")  
   except RedisError:  
     visits = "<i>cannot connect to Redis, counter disabled</i>"  
   html = "<h3>Hello {name}!</h3>" \  
       "<b>Hostname:</b> {hostname}<br/>" \  
       "<b>Visits:</b> {visits}"  
   return html.format(name=os.getenv("NAME", "world"), hostname=socket.gethostname(), visits=visits)  
 if __name__ == "__main__":  
   app.run(host='0.0.0.0', port=80)  

requirements.txt

 Flask  
 Redis  

Note:
When the Dockerfile is built into an image, Dockerfile’s ADD command will add app.py into the image, and the app is served over HTTP with help the EXPOSE command which expose port 80. PIP command install python dependency libraries specified on requirements.txt file

Build the app

Now execute the build command from top of the directory. This creates a Docker image with tag using -t so it has a friendly name.
In my case directory is /Documents/my-docker-img and image name is my-app

 docker build -t my-app .  

To view the list images created on your machine

 docker image ls  

Run the app

Run the app, by mapping your machine’s port 8000 to the container’s published port 80 using -p

 docker run -p 4000:80 friendlyhello  

Then you can access your app deployed within the container using following URL

 http://localhost:8000/  

If you want to run the container in the background in detach mode

 docker run -d -p 4000:80 my-app  

To view all the running containers on your machine

 docker container ls  

If you want to stop the running container using CONTAINER ID

  sudo docker container stop c1081125c6e9   

Next Share your docker image

Useful links
https://docs.docker.com/get-started/part2/#log-in-with-your-docker-id

Installing Docker in Ubuntu

Set up repository to install dependent package for Docker installation

 sudo apt-get update  

Install packages to allow apt to use a repository over HTTPS:

  sudo apt-get install \  
   apt-transport-https \  
   ca-certificates \  
   curl \  
   software-properties-common  

Add Docker’s official GPG key:

 curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -  

To Verify the key with the fingerprint by matching the last 8 characters of the fingerprint.

 sudo apt-key fingerprint 0EBFCD88  

Set up the stable repository I have chosen stable repository and x86_64/amd64. For different version please follow the link

 sudo add-apt-repository \  
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \  
   $(lsb_release -cs) \  
   stable"  

Now to install Docker
Update the apt package index

 sudo apt-get update  

Install the latest version of Docker CE

 sudo apt-get install docker-ce  

To verify that Docker CE is installed correctly by running the hello-world image

 sudo docker run hello-world  

It will download a test image and run it in a container. When the container runs, it prints an informational message and exits. Now Docker CE is installed and running on your machine.

If you need to uninstall Docker installed

 sudo apt-get purge docker-ce  

To delete all images, containers, and volumes which is not removed automatically

 sudo rm -rf /var/lib/docker  

If you want to configure Linux as post installation Click the Link. Some Useful Commands: To see list of images downloaded image on your machine.

 docker image ls  

To get help

 docker container --help  

Next Define your own container with Docker file

Helpful links
https://docs.docker.com/get-started/#conclusion-of-part-one
https://github.com/docker/labs/tree/master/beginner/

JMS implementation

In this example I am creating an JMS implementation of  Point to Point Messaging Domain.

Step 1: Create a simple maven project using you favorite IDE. I am using IntelliJ

Below I have mentioned dependencies required for the project. Add the dependency in your pom.xml

pom.xml

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">  
  <modelVersion>4.0.0</modelVersion>  
  <groupId>com.dipenjms</groupId>  
  <artifactId>JMS</artifactId>  
  <version>1.0-SNAPSHOT</version>  
   <build>  
     <plugins>  
       <plugin>  
         <groupId>org.apache.maven.plugins</groupId>  
         <artifactId>maven-compiler-plugin</artifactId>  
         <configuration>  
           <source>1.7</source>  
           <target>1.7</target>  
         </configuration>  
       </plugin>  
     </plugins>  
   </build>  
   <packaging>jar</packaging>  
  <name>JMS</name>  
  <url>http://maven.apache.org</url>  
  <properties>  
   <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>  
  </properties>  
  <dependencies>  
   <!-- https://mvnrepository.com/artifact/javax.jms/javax.jms-api -->  
   <dependency>  
    <groupId>javax.jms</groupId>  
    <artifactId>javax.jms-api</artifactId>  
    <version>2.0</version>  
   </dependency>  
   <dependency>  
    <groupId>junit</groupId>  
    <artifactId>junit</artifactId>  
    <version>3.8.1</version>  
    <scope>test</scope>  
   </dependency>  
  </dependencies>  
 </project>  

Step 2:
Create a MyReceiver class which is a message consumer.
Note: java:comp/DefaultJMSConnectionFactory in initialContext.lookup() must match name Logical JNDI Name in server and also queue name.

MyReceiver.java

 package javatpoint.dipen.jms;  
 import javax.jms.*;  
 import javax.naming.InitialContext;  
 import javax.naming.NamingException;  
 /**  
  * Created by dipen on 5/5/2017.  
  */  
 public class MyReceiver {  
   public static void main(String[] args) {  
     try {  
       InitialContext initialContext = new InitialContext();  
       QueueConnectionFactory queueConnectionFactory= (QueueConnectionFactory) initialContext.lookup("java:comp/DefaultJMSConnectionFactory");  
       QueueConnection queueConnection = queueConnectionFactory.createQueueConnection();  
       queueConnection.start();  
       QueueSession queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);  
       Queue queue = (Queue) initialContext.lookup("myQueue");  
       QueueReceiver queueReceiver = queueSession.createReceiver(queue);  
       final TextMessage[] textMessage = new TextMessage[1];  
       queueReceiver.setMessageListener(   new MessageListener(){  
         @Override  
         public void onMessage(Message message) {  
           System.out.print("Inside Message Receiver" + message);  
           textMessage[0] = (TextMessage) message;  
         }  
       });  
       System.out.print(textMessage[0]);  
       queueConnection.close();  
     } catch (NamingException | JMSException e) {  
       e.printStackTrace();  
     }  
   }  
 }  

Step 3:
Create a MySender class which is a message producer.

MySender.java

 package javatpoint.dipen.jms;  
 import javax.jms.*;  
 import javax.naming.Context;  
 import javax.naming.InitialContext;  
 import javax.naming.NamingException;  
 import javax.xml.soap.Text;  
 import java.util.Properties;  
 /**  
  * Created by dipen on 5/5/2017.  
  */  
 public class MySender {  
   public static void main(String[] args) {  
     Properties env = new Properties( );  
     env.put(Context.INITIAL_CONTEXT_FACTORY,  
         "com.sun.jndi.fscontext.RefFSContextFactory");  
     /* env.put(Context.PROVIDER_URL,  
         "ts://localhost:4848");*/  
     try {  
       InitialContext initialContext = new InitialContext();  
       QueueConnectionFactory queueConnectionFactory= (QueueConnectionFactory) initialContext.lookup("java:comp/DefaultJMSConnectionFactory");  
       QueueConnection queueConnection = queueConnectionFactory.createQueueConnection();  
       queueConnection.start();  
       QueueSession queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);  
       Queue queue = (Queue) initialContext.lookup("myQueue");  
       QueueSender queueSender = queueSession.createSender(queue);  
       TextMessage textMessage = queueSession.createTextMessage();  
       textMessage.setText("Hello Dipen! This is JMS Testing");  
       queueSender.send(textMessage);  
       queueConnection.close();  
     } catch (NamingException | JMSException e) {  
       e.printStackTrace();  
     }  
   }  
 }  

Step 4:
Install  Glassfish4 Server from official site or Click Here and unzip in your desired directory.
Note: Download Java EE 7 Full Platform version.

Open bin directory from recently extracted Server directory and run asadmin.bat
For me it is: F:\IDE\Servers\glassfish4\bin

Then start the server using the command: start-domain

Now on your browser load the server admin page :http://localhost:4848/common/index.jsf

Step 5:
Click on the JMS Resource -> Connection Factories -> New, now write the pool name and select the Resource Type as QueueConnectionFactory then click on ok button.

Click on the JMS Resource -> Destination Resources -> New, now write the JNDI name and physical destination name then click on ok button.

Step 6: Run both MySender and MyReceiver.

Note : If there is error while running the project, add javaee.jar and appserv-rt.jar into your library from <yourpath>\glassfish\lib
For me it's: F:\IDE\Servers\glassfish4\glassfish\lib

Sender output

Receiver output

Download Source for GitHub : Click Here

Installing and setting Java path

Download Java
Download lastest release of java form the official site

http://www.oracle.com/technetwork/java/javase/downloads/index.html
 Install the downloaded file
The file is installed into follwing location C:\Program Files\Java
Then, right click on mycomputer

 -> click properties -> the follwing screen will be displayed

 Now, click on Advance System Setting, screen below appears

 Click on Envirnment Variables, another window is displayed

 Click New button below the upper box and secreen below will be displayed

Insert following into corrosponding textbox
Variable name: JAVA_HOME
Variable Value: C:\Program Files\Java\jdk1.7.0_07

In lower box select Path and click Edit button, at the end after “;” paste full path to bin folder (Note :- keep other content in box as it is and end the line with “;”)
Variable Value: C:\Program Files\Java\jdk1.7.0_07\bin;

Now, after all this process check that Java installation and setting is successfully completed
Open command  and run follwing syntax
C:\Java -version and you will see screen below if all the setting are correct

Check code quality with PMD

Integrating PMD plugin on STS (subclipse) /Eclipse

1. Open STS  -> click on Help

2. Click ->Install New software

3. Click Add Button and screen blow is dispalyed
Name : PMDplugin
Location: http://sourceforge.net/projects/pmd/files/pmd-eclipse/update-site/

4. Check on PMD for Eclipse 3.

5. Click -> Next

6. Agree the agreement and click -> Finish

7. Wait for Eclipse to download the required jar files, then click Install
8. Restart the workbench. This will load the PMD plugin.
9. Navigate to Window | Show View | Other...

10. Select PMD |select -> Violations overview

Opearating  PMD in STS  (How to usePMD)
1. In the Package Explorer right-click on Project and select PMD | Check Code With PMD

2. PMD Violations view notice a list of violations

Installing TortoiseSVN and integrating with STS

Install TortoiseSVN

1. Download TortoiseSVN from following link ( download the latest stable release of TortoiseSVN)
http://tortoisesvn.net/downloads.html

1. Click and run the downloaded file, continue the installation process

Using TortoiseSVN client on Windows
 
Verifying Installation:
In order to verify the successful installation of the Tortoise SVN client right click on any folder and you can see the TORTOISE SVN TASKS as shown below:

Check out from SVN Repository:
Step1: create the folder where you want to check out the files/folder from SVN server repository.
Step2: right click the folder and click on SVN Checkout. Now you can see the screen like Figure 1.

Figure 1: SVN Check out screen
Step 3: In above picture Figure 1. URL is the SVN server repository url to access the files and the Checkout directory is the directory where you are going to download (checkout) the files. After specifying the url and directory click OK.
Step4: After step 3 you may be asked for your SVN username and password. Enter the valid username and password and proceed.
Step 4: now you can see the files checkout from the SVN server repository as shown below figure 2

Figure 2: checkout from svn screen
 
Configuring TortoiseSVN
TortoiseSVN generally requires no configuration. To access a repository, a checkout operation should be performed. Right-click in the directory to perform the checkout, and select 'SVN Checkout' from the menu. Then, access the repository via URL, similar to how a web-browser operates. This URL will look like:
https://PROJECTNAME.svn.sourceforge.net/svnroot/PROJECTNAME
Though, typically you would want to specify the trunk to be checked out. Like this:
https://PROJECTNAME.svn.sourceforge.net/svnroot/PROJECTNAME/trunk
PROJECTNAME is the project UNIX name, as specified on the summary page for the project in question. The project, 'filezilla', for example, would use the following URL to checkout the trunk of their SVN repository:
https://filezilla.svn.sourceforge.net/svnroot/filezilla/trunk
Upon first connection to the SourceForge.net SVN server, you may be prompted to accept the 'server certificate' for svn.sourceforge.net, you should 'Accept Permanently' the certificate.
After initial checkout, if you change a file and want to commit the change back to the repository, you will be prompted for your username and password. This will be the username and password for the SourceForge.net website.
Example:


Integrating TortoiseSVN client on STS (subclipse)

1. Open STS  -> click on Help

2. Click ->Install New software

3. Click Add Button and screen blow is dispalyed
Name : trotoiseSvn
Location: http://subclipse.tigris.org/update_1.10.x
For further information visit
http://subclipse.tigris.org/servlets/ProjectProcess?pageID=p4wYuA

4. STS automatically downloads all the required plugins, after that restart the STS and refer to section below for the tips to operate the plugin.

Opearating  subclipse from STS

1. Right click on Project Explorer and

2. click -> Import

3. Choose SVN menu and  click -> checkout Projects for SVN  -> Next Button
4. If its first time select first option then -> Next Button
Provide the link of your SVN server  -> Next Button
i.e. my current server location is https://windows-2kj6rz/svn/

Else you are provided with list of projects from previous server setting and choose a project to work on.
5. After that following screen will be displayed, choose appropriate folder and project you want and click -> Next Button


6. If you want further setting  modify as you need, but for our purpose default is alright thus -> Finish Button

Set default selected value in struts2 select tag

Setting selected date in dojo date picker using struts2.

Add the code below in jsp file.

      <!--name attribute inside select tag must be a variable in action class with getter/setter -->  
      <!-- test variable sets the value of selected item in action class -->  
      <select name="test">  
           <!-- name attribute could be anything you want but value attribute must be a model class variable-->  
           <s:set name="lead_string_LS_ID" value="MasterDataModel.string_LS_ID" />  
                <!-- value attribute must be a list to iterate, status (an instanceof IteratorStatus will be pushed into stack upon each iteration)or result -->  
                <!-- var Name used to reference the value pushed into the Value Stack (my list contain leadSource_String_Id)-->  
                <s:iterator value="leadSource_list" status="result" var="leadSource_String_Id">  
                          <!--#lead_string_LS_ID is value taken from <set> tag above. Note # must be in-front of the name  
                               leadSource_String_Id is element specified in var of <iterator> tag       
                          -->  
                          <s:if test='(#lead_string_LS_ID.equals(leadSource_String_Id))'>  
                               <option value="<s:property value='leadSource_String_Id'/>" selected="selected">  
                                    <s:property value="leadSource_String_Name" />  
                               </option>  
                          </s:if>  
                          <s:else>  
                               <option  
                                    value="<s:property value='leadSource_String_Id'/>">  
                                    <s:property value="leadSource_String_Name" />  
                               </option>  
                          </s:else>  
                </s:iterator>  
      </select>  

Android Form Validation

This example show how to prevent null and blank field. Here username field check whether the submitted value is null or some blank space. If the submitted value is null or blank it displays a error message. Another amount field prevent user from entering negative value in the field, it simply uses android:inputType="numberDecimal" to prevent user to enter negative value. Likewise you can limit input size with android:maxLength="20", this limits text size to 20 characters.

Click Here to download Source Code

Fig: Form Validation

FormValidationExampleActivity.java

 package com.rnd.action;  
 import java.util.regex.Matcher;  
 import java.util.regex.Pattern;  
 import android.app.Activity;  
 import android.os.Bundle;  
 import android.util.Log;  
 import android.view.View;  
 import android.widget.Button;  
 import android.widget.EditText;  
 import android.widget.Toast;  
 public class FormValidationExampleActivity extends Activity{  
   /** Called when the activity is first created. */  
      EditText username, amount;  
       Button btn;  
      @Override  
   public void onCreate(Bundle savedInstanceState)  
      {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.main);  
        username = (EditText) findViewById(R.id.username);  
     amount = (EditText) findViewById(R.id.amount);  
        btn = (Button) findViewById(R.id.button1);  
     btn.setOnClickListener(new View.OnClickListener() {  
                public void onClick(View v) {  
                     Log.d("Checking value of textbox", amount.getText().toString());  
               if(formValidator(username.getText().toString()) == true)  
               {  
                    Toast.makeText(FormValidationExampleActivity.this, "Valid Data", Toast.LENGTH_LONG).show();  
               }  
               else  
               {  
                    Toast.makeText(FormValidationExampleActivity.this, "Name field is required", Toast.LENGTH_LONG).show();  
               }  
                }  
           });  
      }  
      public boolean formValidator(String values)  
      {  
           if((values.trim()).equals("") || values.equals(null))  
           {  
                return false;  
           }  
           else  
           {  
                return true;  
           }  
      }  
      public void checkemail(String email)  
      {  
        Pattern pattern = Pattern.compile(".+@.+\\.[gmail.com]+");  
        Matcher matcher = pattern.matcher(email);  
        boolean emailcheck = matcher.matches();  
      }  
 }  

Main.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
   android:layout_width="fill_parent"  
   android:layout_height="fill_parent"  
   android:orientation="vertical" >  
   <TextView  
     android:layout_width="fill_parent"  
     android:layout_height="wrap_content"  
     android:text="@string/hello" />  
   <EditText  
     android:id="@+id/username"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:ems="10"  
      >  
     <requestFocus />  
   </EditText>  
   <EditText  
     android:id="@+id/amount"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:ems="10"  
     android:inputType="numberDecimal" />  
   <Button  
     android:id="@+id/button1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Ok" />  
 </LinearLayout>  

Android ListView onItemClick Event

Here are the output screen of the application where users are able to insert their data through a textbox by clicking ok button as shown in image below. After adding the items users are able to select the items via clicking on it and the selected item is displayed via a toast.

Click Here to download source folder

 

ListExampleActivity.java

 package com.rnd.action;  
 import java.util.ArrayList;  
 import android.app.Activity;  
 import android.os.Bundle;  
 import android.util.Log;  
 import android.util.SparseBooleanArray;  
 import android.view.KeyEvent;  
 import android.view.MotionEvent;  
 import android.view.View;  
 import android.widget.AdapterView;  
 import android.widget.ArrayAdapter;  
 import android.widget.Button;  
 import android.widget.EditText;  
 import android.widget.ListView;  
 import android.widget.Toast;  
 public class ListExampleActivity extends Activity {  
   /** Called when the activity is first created. */  
   ListView lv;  
   String[] outputStrArr;  
   ArrayAdapter<String> aa = null;  
      @Override  
   public void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.main);  
     lv = (ListView) findViewById(R.id.listView_user);  
     final EditText myEditText = (EditText) findViewById(R.id.myeditText);  
     final ArrayList<String> todoItems = new ArrayList<String>();  
     aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,todoItems);  
     lv.setAdapter(aa);  
     myEditText.setOnKeyListener(new View.OnKeyListener() {  
                public boolean onKey(View v, int keyCode, KeyEvent event) {  
                     // TODO Auto-generated method stub  
                     if(event.getAction()== KeyEvent.ACTION_DOWN)  
                     {  
                          if(keyCode == KeyEvent.KEYCODE_DPAD_CENTER)  
                          {  
                               todoItems.add(0,myEditText.getText().toString());  
                               aa.notifyDataSetChanged();  
                               myEditText.setText("");  
                               return true;  
                          }  
                     }  
                     return false;  
                }  
           });  
     lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {  
                public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,  
                          long arg3) {  
                     //Log.i("Selected Item in list", arg1.toString());  
                     String test = (String) lv.getAdapter().getItem(arg2);  
                     Log.i("Selected Item in list", test);  
                     Toast.makeText(ListExampleActivity.this,test ,Toast.LENGTH_LONG);  
                }  
           });  
     }  
 }  

Main.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
   android:layout_width="fill_parent"  
   android:layout_height="fill_parent"  
   android:orientation="vertical" >  
   <TextView  
     android:layout_width="fill_parent"  
     android:layout_height="wrap_content"  
     android:text="@string/hello" />  
   <EditText  
     android:id="@+id/myeditText"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:ems="10" >  
     <requestFocus />  
   </EditText>  
   <ListView  
     android:id="@+id/listView_user"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:clickable="true"   
      >  
   </ListView>  
 </LinearLayout>  

 

AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
   package="com.rnd.action"  
   android:versionCode="1"  
   android:versionName="1.0" >  
   <uses-sdk android:minSdkVersion="8" />  
   <application  
     android:icon="@drawable/ic_launcher"  
     android:label="@string/app_name" >  
     <activity  
       android:name=".ListExampleActivity"  
       android:label="@string/app_name" >  
       <intent-filter>  
         <action android:name="android.intent.action.MAIN" />  
         <category android:name="android.intent.category.LAUNCHER" />  
       </intent-filter>  
     </activity>  
   </application>  
 </manifest>  

List with checkbox

Here are the output screen of the application where users are able to insert their data through a textbox by clicking ok button as shown in image below. After adding the items users are able to select the items via a checkbox and the selected item are only rendered back to list when the button appearing on screen is clicked. 

Fig: Android List with checkbox

Fig:

Get Selected Item Using Checkbox in Listview when Button is clicked

Click Here to download source folder
 

ListCheckboxExampleActivity.java

 package com.rnd.action;  
 import java.util.ArrayList;  
 import android.app.Activity;  
 import android.os.Bundle;  
 import android.util.Log;  
 import android.util.SparseBooleanArray;  
 import android.view.KeyEvent;  
 import android.view.View;  
 import android.widget.ArrayAdapter;  
 import android.widget.Button;  
 import android.widget.EditText;  
 import android.widget.ListView;  
 public class ListCheckboxExampleActivity extends Activity {  
   /** Called when the activity is first created. */  
   ListView lv;  
   String[] outputStrArr;  
   ArrayAdapter<String> aa = null;  
      @Override  
   public void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.main);  
     lv = (ListView) findViewById(R.id.listView_user);  
     final EditText myEditText = (EditText) findViewById(R.id.myeditText);  
     final ArrayList<String> todoItems = new ArrayList<String>();  
     aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice,todoItems);  
     lv.setAdapter(aa);  
     myEditText.setOnKeyListener(new View.OnKeyListener() {  
                public boolean onKey(View v, int keyCode, KeyEvent event) {  
                     // TODO Auto-generated method stub  
                     if(event.getAction()== KeyEvent.ACTION_DOWN)  
                     {  
                          if(keyCode == KeyEvent.KEYCODE_DPAD_CENTER)  
                          {  
                               todoItems.add(0,myEditText.getText().toString());  
                               aa.notifyDataSetChanged();  
                               myEditText.setText("");  
                               return true;  
                          }  
                     }  
                     return false;  
                }  
           });  
     Button btn_ok = (Button) findViewById(R.id.button_ok);  
     btn_ok.setOnClickListener(new View.OnClickListener() {  
                public void onClick(View v) {  
                     SparseBooleanArray checked = lv.getCheckedItemPositions();  
               ArrayList<String> selectedItems = new ArrayList<String>();  
               for (int i = 0; i < checked.size(); i++) {  
                 // Item position in adapter  
                 int position = checked.keyAt(i);  
                 // Add sport if it is checked i.e.) == TRUE!  
                 if (checked.valueAt(i))  
                   selectedItems.add(aa.getItem(position));        
               }  
               outputStrArr = new String[selectedItems.size()];  
               aa.clear();  
               for (int i = 0; i < selectedItems.size(); i++) {  
                 outputStrArr[i] = selectedItems.get(i);  
                 Log.i("test data" + outputStrArr[i], null, null);  
                 aa.add(selectedItems.get(i));  
               }  
                }  
           });  
   }  
 }  

main.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
   android:layout_width="fill_parent"  
   android:layout_height="fill_parent"  
   android:orientation="vertical" >  
   <TextView  
     android:layout_width="fill_parent"  
     android:layout_height="wrap_content"  
     android:text="@string/hello" />  
   <EditText  
     android:id="@+id/myeditText"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:ems="10" >  
     <requestFocus />  
   </EditText>  
   <ListView  
     android:id="@+id/listView_user"  
     android:layout_width="match_parent"  
     android:layout_height="wrap_content"  
     android:choiceMode="multipleChoice"  
      >  
   </ListView>  
   <Button  
     android:id="@+id/button_ok"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="Button" />  
 </LinearLayout>  

AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
   package="com.rnd.action"  
   android:versionCode="1"  
   android:versionName="1.0" >  
   <uses-sdk android:minSdkVersion="8" />  
   <application  
     android:icon="@drawable/ic_launcher"  
     android:label="@string/app_name" >  
     <activity  
       android:name=".ListCheckboxExampleActivity"  
       android:label="@string/app_name" >  
       <intent-filter>  
         <action android:name="android.intent.action.MAIN" />  
         <category android:name="android.intent.category.LAUNCHER" />  
       </intent-filter>  
     </activity>  
   </application>  
 </manifest>