Java ~ Jeopardy

2012-01-04T07:47:00.001-08:00

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Read & Write file using java I/O Stream.

2010-12-22T05:24:00.000-08:00

/**
* Created by IntelliJ IDEA.
* User    : Rajesh.Muralidharen - therajguru06@gmail.com
* Date    : Dec 22, 2010
* Time    : 6:09:46 PM
* Delimit : Read & Write file using java I/O Stream.
*           This example shows how to read and write a file using Java I/O Stream package
*           FileInputStream is used to read binary content of the file and
*           return bytes of data.
*           FileOutputStream is used to write bytes content into a file in the declared location.
*/
import java.io.*;

public class FileInputOutputStreamExample {

    public void readFile(){
        int ch;
        File filePath = new File("D:\\Inputfile.txt");
        StringBuffer strContent = new StringBuffer("");
        FileInputStream fin = null;

        try {
            fin = new FileInputStream(filePath);
            while( (ch = fin.read()) != -1)
            strContent.append((char)ch);
            fin.close();
            System.out.println("Read successfully completed...");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            System.out.println(filePath.getAbsolutePath());
        } catch (IOException e) {
            e.printStackTrace();
        }
        //command-out the below code to get the read contents!
        //System.out.println(strContent);
        writeFile(strContent); //invoking Write file.
    }

    public void writeFile(StringBuffer strContent){
        String getName = (String) strContent.toString();
        try {
            FileOutputStream fou = new FileOutputStream("D:\\Outputfile.txt");
            fou.write(getName.getBytes());
            fou.flush();
            fou.close();
            System.out.println("Write successfully completed...");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
           FileInputOutputStreamExample fiose = new FileInputOutputStreamExample();
           fiose.readFile(); //invoking Read File.
    }
}

Setting up a Servlet development environment in Servlet Tutorials

2010-05-24T22:19:00.000-07:00

This tutorial provides step by step instructions to setup the development environment required to test various servlet examples given throughout all the tutorials. This tutorial will also be helpful when you start practicing servlets yourself.

List of required softwares:

JAVA 1.5 or 1.6

Tomcat 5.5.16

eclipse 3.3

Note: this tutorial explains how to install required software on your windows based PC only.

First of all you need the Java software development kit 1.5 or 1.6 (JAVA SDK) installed.
Checking if JAVA is already installed in your system

Follow this step to check if Java software development kit (JDK) is already installed in your system.

To determine if JAVA SDK is already installed in your system, run the following command from command prompt.
Java –version

If JAVA platform is already installed, it will display the version of the JAVA SDK. Below screen shows JAVA version 1.6 running on a windows system. If command executes successfully and shows JAVA version 1.6, you can skip the next step.otherwise download and install the Java SDK as explained in next step.

Install JAVA SDK

First thing you need to install is Java software development kit (Java SDK) .Download the Java development kit 6 (JDK 6) from Sun Java SE Download site. Current latest version is JDK 6 update 6.
Set up the JAVA_HOME environment variable

Once the JAVA SDK is installed follow this step to set the JAVA_HOME environment variable. If JAVA_HOME variable is already set, you can skip this step.

Right click on My Computer icon on your desktop it will open a popup menu, click on properties, it will open the system properties window, then click on advanced tab.

Click on environment variables button, it will open the environment variables window as shown in figure below. Initially there will be no JAVA_HOME environment variable set as shown in figure.

Click on new button to add new system variable JAVA_HOME.

In the variable name filed, enter JAVA_HOME. Specify the path to root directory of JAVA installation in variable value field and click OK button. Now JAVA_HOME will appear under user variables.

Next you need to add bin directory under the root directory of JAVA installation in PATH environment variable.Select the PATH variable from System variables and click on Edit button.

Add: ;%JAVA_HOME%\bin; at the end of variable value field and click OK button.

Now verify that everything is correct by following the step: Checking if JAVA is already installed in your system. It should show the version of the installed JAVA SDK.
Installing Tomcat

Tomcat is an opensource web container. it is also web container reference implementation. You will need tomcat 5.5.16 installed on your system to test various servlet and JSP examples given in other tutorials.

Download the latest version of tomcat from this URL . Download the jakarta-tomcat-5.0.28.tar.gz and extract it to the directory of your choice.

Note: This directory is referred as TOMCAT_HOME in other tutorials.

That’s all, tomcat is installed. It’s very easy, isn’t it?
Starting and shutting down Tomcat

To start the tomcat server, open the command prompt, change the directory to TOMCAT HOME/bin and run the startup.bat file. It will start the server.
>startup

To shut down the tomcat server, run the shutdown.bat file. It will stop the server.
>shutdown
Verifying Tomcat installation

To verify that tomcat is installed properly, start the server as explained above, open the web browser and access the following URL.

http://localhost:8080/index.jsp

It should show the tomcat welcome page, if tomcat is installed properly and server is running.
Setting up the CLASSPATH

Now you need to create a new environment variable CLASSPATH if it is not already set. We need to add the servlet-api.jar into the CLASSPATH to compile the Servlets. Follow the same steps as you did to create the JAVA_HOME variable. Create a new variable CLASSPATH under system variables. Add TOMCAT_HOME/lib/servlet-api.jar in variable value field.

Note: here TOMCAT_HOME refers to the tomcat installation directory.

Inheritance *entends

2010-05-24T22:17:00.000-07:00

/*Java Inheritance*/

class tuttu{

void tuttu_display(){

System.out.print("Shapes\n");

}

class Rectangle extends tuttu{

private int l = 2;

private int b = 3;

void display(){

System.out.print("\nArea of Rectangle" + (l*b)+"then\n");

}

class Circle extends Rectangle {

private int r = 4;

void display(){

System.out.print("\nArea of Circle" + (3.14f*r*r)+"then\n");

}

class Square{

private int a = 5;

void display(){

System.out.print("\nSquare" + (a*a)+"then\n");

}

class demo{

public static void main(String args[]){

Rectangle rect = new Rectangle();

rect.tuttu_display();

rect.display();

Circle cri = new Circle();

cri.display();

cri.tuttu_display();

Square squ = new Square();

squ.display();

}

Thread?

2010-05-24T22:15:00.003-07:00

/*Simple thread pgm*/

class ParentThread{
    public static void main(String args[]) throws InterruptedException{
        try{
        for(int i=0;i<=5;i++){
            System.out.print("\n Parent thread "+i);
            Thread.sleep(1000);
            }
        }catch(InterruptedException ie){
        System.out.print("Sleep Method Invoked");
            }
    }
}

output:

Parent thread 0
Parent thread 1
Parent thread 2
Parent thread 3
Parent thread 4
Parent thread 5

Naming a Thread?

2010-05-24T22:15:00.001-07:00

/*Give name to Thread*/

class ParentThread{

public static void main(String args[]) throws InterruptedException{

Thread t = Thread.currentThread();

System.out.print(t+"\n");

t.setName("MyThread");

System.out.print(t.getName()+"\n");

System.out.print(t);

}

output:
Thread[main,5,main]
MyThread
Thread[MyThread,5,main]

Thread Concept!!!

2010-05-24T22:14:00.001-07:00

/*Multithreading with extends Thread*/

class ChildThread extends Thread{
    public void run(){
        System.out.print("Child thread started...\n");
        for(int i=11;i<=15;i++){
            System.out.print("\n Child thread "+i);
            try{
                Thread.sleep(2000);
            }catch(InterruptedException ie){
                System.out.print(ie);
            }
        }//for ends
    }//Method ends.
}//Class ends.

class ParentThread{
    public static void main(String args[]) throws InterruptedException{
        ChildThread ct = new ChildThread();
        ct.start();
        System.out.print("Parent thread started...\n");
        for(int i=1;i<=5;i++){
            System.out.print("\n Parent Thread "+i);
            Thread.sleep(2000);
        }
    }
}

output:
Parent thread started...

Parent Thread 1Child thread started...

Child thread 11
Parent Thread 2
Child thread 12
Parent Thread 3
Child thread 13
Child thread 14
Parent Thread 4
Child thread 15
Parent Thread 5

User Defined Exception.

2010-05-24T22:13:00.002-07:00

/*For user defined exception*/

class ValidVoter extends Exception
{
//    private static final long serialVersionUID = 1L;

    public String toString(){
        return "Invalid Voter";
    }
}
class tuttu{
    public static void main(String args[]){
        ValidVoter vv = new ValidVoter();
        int age = 17;
        try{
            if(age < 18){
                throw vv;
            }else{
                    System.out.print("Valid Voter");
            }
            }catch(ValidVoter vv1){
                System.out.print(vv1);
            }
    }//Main ends.
}//demo ends

Try Block in java Exception

2010-05-24T22:13:00.000-07:00

/*try block*/

class try_catch_eg{
    public static void main(String args[]){
        //try{
        int a = 1;
        System.out.print("The solution is "+ (a/0));
        //}catch(Exception e){
            //System.out.print("Exception is "+e);
        //}
    }
}

output :

err: Exception in thread "main" java.lang.ArithmeticException: / by zero
    at try_catch_eg.main(try_catch_eg.java:6)

Inheritance *entends

2010-05-24T22:12:00.001-07:00

/*Java Inheritance*/

class tuttu{
    void tuttu_display(){
        System.out.print("Shapes\n");
    }
}
class Rectangle extends tuttu{
    private int l = 2;
    private int b = 3;
    void display(){
        System.out.print("\nArea of Rectangle" + (l*b)+"then\n");
    }
}
class Circle extends Rectangle {
    private int r = 4;
    void display(){
        System.out.print("\nArea of Circle" + (3.14f*r*r)+"then\n");
    }
}
class Square{
    private int a = 5;
    void display(){
        System.out.print("\nSquare" + (a*a)+"then\n");
    }
}
class demo{
    public static void main(String args[]){

    Rectangle rect = new Rectangle();
    rect.tuttu_display();
    rect.display();

    Circle cri = new Circle();
    cri.display();
    cri.tuttu_display();

    Square squ = new Square();
    squ.display();
    }
    }

Final in java.

2010-05-24T22:11:00.001-07:00

/*"final " usage in java*/

class Base{
    public String x;

    final void display(){
        int x = 50;
        System.out.print("\nprint "+ x);
    }
}
class Derived extends Base{
    void display(){
        int x= 100;
        System.out.print("print "+ x);
    }
}
class demo{
    public static void main(String args[]){
        Derived d = new Derived();
        d.display();
    }
}

Java in Method Over Loading.

2010-05-24T22:10:00.001-07:00

/*Method overloading*/

class Base{
    void display(){
        System.out.print("Base class...");
    }
}
class Derived extends Base{
    void display(){
        System.out.print("Derived class...");
    }
}
class demo{
    public static void main(String args[]){
        Derived d = new Derived();
        d.display();
    }
}

Getting the Ip address of your PC?

2010-05-22T20:52:00.001-07:00

/*How to get the ip add*/

import java.net.*;

public class tuttu{

public static void main(String [] args) {

try {

InetAddress addr = InetAddress.getLocalHost();

byte[] ipAddr = addr.getAddress();

String hostname = addr.getHostName();

System.out.println("hostname="+hostname);

System.out.println("ipAddress="+ipAddr);

} catch (UnknownHostException e) {

}

Alternative:

import java.net.*;

import java.io.*;

public class GetIPAddress {

public static void main(String [] args) {

try {

InetAddress thisIp =InetAddress.getLocalHost();

System.out.println("IP:"+thisIp.getHostAddress());

}

catch(Exception e) {

e.printStackTrace();

}

Get PC - User name in java?

2010-05-22T20:50:00.000-07:00

/*Get computer name in java*/

import java.util.*;

import java.lang.*;

import java.net.*;

public class GetComputerName

{

public static void main(String args[]) {

try{

String computername=InetAddress.getLocalHost().getHostName();

System.out.println(computername);

}catch (Exception e){

System.out.println("Exception caught ="+e.getMessage());

}

Get the Clipboard from system?

2010-05-22T20:49:00.003-07:00

/*Java Get Clipboard*/

import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

import java.awt.datatransfer.*;

public class tuttu {

public static void main(String args[]) {

JFrame frame = new JFrame("Use Clipboard");

final Clipboard clipboard =

frame.getToolkit().getSystemClipboard();

final JTextArea area = new JTextArea();

frame.add(area, BorderLayout.CENTER);

JButton copy = new JButton("Copy");

copy.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String selection = area.getSelectedText();

StringSelection data = new StringSelection(selection);

clipboard.setContents(data, data);

}

});

JButton paste = new JButton("Paste");

paste.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent actionEvent) {

Transferable clipData = clipboard.getContents(clipboard);

try {

if(clipData.isDataFlavorSupported(DataFlavor.stringFlavor)) {

String s = (String)(clipData.getTransferData(DataFlavor.stringFlavor));

area.replaceSelection(s);

}

} catch (Exception ufe) {}

}

});

JPanel p = new JPanel();

p.add(copy);

p.add(paste);

frame.add(p, BorderLayout.SOUTH);

frame.setSize(300, 200);

frame.setVisible(true);

}

how to get the Current date display in java?

2010-05-22T20:48:00.001-07:00

/*Get date & time*/

import java.util.Calendar;

import java.text.SimpleDateFormat;

public class DateAndTime {

public String date = "yyyy-MM-dd HH:mm:ss";

public static now()

{

Calendar calendar = Calendar.getInstance();

SimpleDateFormat dateFormat = new SimpleDateFormat(date);

return dateFormat.format(calendar.getTime());

}

public static void main(String arg[])

{

now();

System.out.println("Date and Time : " +DateAndTime .now());

}

How to Capitalize the first letter of the String?

2010-05-22T20:47:00.001-07:00

/*Making the first as capital*/

import javax.swing.*;

public class tuttu {

public static void main(String[] args) {

//.. Input a word

String inputWord = JOptionPane.showInputDialog(null, "Enter a word");

//.. Process - Separate word into parts, change case, put together.

String firstLetter = inputWord.substring(0,1); // Get first letter

String remainder = inputWord.substring(1); // Get remainder of word.

String capitalized = firstLetter.toUpperCase() + remainder.toLowerCase();

//.. Output the result.

JOptionPane.showMessageDialog(null, capitalized);

}

How to use Console in java for getting input?

2010-05-22T20:46:00.001-07:00

/*Get input from the console & display*/

import java.util.Scanner;

public class tuttu {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

// Read string input for username

System.out.print("Username: ");

String username = scanner.nextLine();

// Read string input for password

System.out.print("Password: ");

String password = scanner.nextLine();

// Read an integer input for another challenge

System.out.print("What is 2 + 2: ");

int result = scanner.nextInt();

if (username.equals("admin") && password.equals("secret") && result == 4) {

System.out.println("Welcome to Java Application");

} else {

System.out.println("Invalid username or password, access denied!");

}

String

2010-05-22T20:45:00.000-07:00

/*To get the reverse of the String*/

public class StringReverseExample {

public static void main(String[] args) {

// TODO Auto-generated method stub

String strOriginal = "MalayalaM";

System.out.println("Original String : " + strOriginal);

strOriginal = new StringBuffer(strOriginal).reverse().toString();

System.out.println("Reversed String : " + strOriginal);

}

Java is simple!

2010-04-17T00:11:00.000-07:00

     We need a console application for commanding the java complier
     to get works.For that we can make use of 'Commad prompt',before
     that make sure that you have set the environment variables.
     The note pad(your source codec with classname and java extension)
     should be saved in the bin folder in jdk,so that the java
     complier automatically takes the class name of the notepad.If keeping
     the java notepad in bin directory then we have to set path everytime
     when we want to get compile a java code.

     set path=c:\j2sdk1.4.1_01\bin
     before using the 'javac filename.java' and 'java filename'

     Else you can set the environment varialbes so that you can keep your
     java code anywhere and compile it.
     1) By default the jdk installed in C: drive.Get the path of the bin directory
        in your jdk folder.It wil look something like this.

      -> eg: C:\ProgramFiles\Java\Jdk\bin
          now copy the url of ur bin directory

   2)Right click My Computer->Properties->Advanced Settings->Environment Variables->System Variables->Select 'Path' variable now paste it starting with a ';'
         Semicolon.It will look something like this

           -> ;C:\ProgramFiles\Java\Jdk\bin

     3) Once you have set this path you can see these for verification in you
         cmd prompt(run) by typing
         ->         path

          where you can see the pasted url of bin directory in it!

      Writing a code & saving it...?
       eg:
    class example {
     public static void main(String args[])
                           {
       System.out.println("This is the first Example in java Program after installing JDK");
                }
                      }
         -> Here the class name is 'example',so save the classname for the notepad like 'example.java'
             in any drive.
         -> The extension is really important.If you have saved the notepad only with 'example', it wil
             get saved in txt format which is not recognized by java compiler.

       4) Now you are ready for compilation! Goto cmd type the drive or directory path were you have
            saved the java program 'example'
           -for eg: location like D:/My_files/JavaPgms/(paht of 'example.java')

       5) After getting into the path type
            -> javac example.java
            -> javac(javacompliation) example(filename).java(extension)

            it wil take few time based upon your ram speed like nano secs!
            Then type
             -> java example
             -> java(console app name) example(filename)
            then you will get the o/p as - This is the first Example in java Program after installing JDK

Hope you got a basic idea about java config & compliation!!!

Configuring Eclipse to use Tomcat and the Spring Framework

2010-01-25T20:48:00.000-08:00

Configuring Eclipse to use Tomcat and the Spring Framework

There never seems to be enough documentation on how to create Spring Framework enabled projects in Eclipse. Spring is widely used for web applications so you need to know how to integrate Tomcat and Eclipse as well - so there is even less documentation! There follows below a step-by-step set of instructions to do just that.

I am not going to describe how to install the Java Runtime environment. If you need help with that, then maybe web services is not the career you should be focusing on ;) Needless to say it is a requirement of all the following technologies.

Installation
Windows is (not) funny about spaces in directory names so all the installations will be located under c:\java instead of c:\Program Files. You’ll save yourselves an enormous headache trying to figure out why Windows is not interpreting the command lines properly if you just remove the cause of the problem. Bloody Bill!

Download Eclipse IDE for Java EE Developers 3.4 Ganymede from the downloads section of the Eclipse web site.

1.Extract the eclipse-jee-ganymede-win32.zip into c:\Java\eclipse.
2.Create a desktop shortcut to the Eclipse executable, for easy launching.
3.Download Tomcat 6.x from the downloads section of the Tomcat web site. You will need to get the base (Core) pack and not the windows installer pack. The windows installer pack does not include some of the command-line scripts for launching Tomcat.
4.Extract the apache-tomcat-6.0.18.zip into c:\java\apache-tomcat-6.0.18 then rename it to c:\java\tomcat.
5.Launch Eclipse.
6.On a new install of Eclipse it asks you where you want to put your workspace. We are going to place it in c:\java\workspace because the spaces issue will be a problem if it goes into c:\Documents and Settings\David Newcomb\workspace.
7.Next we are going to install our Spring IDE plugin, full instructions on how to do this are on my blog page entitled Eclipse 3.4 Ganymede and Spring IDE 2.0.6.
8.After installation it says It is strongly recommended you restart your system for the changes to take effect. .. Restart now?, when it says system it means the eclipse workbench and not your whole computer, so click Yes.

Configure Tomcat inside Eclipse
1.Next we need to tell Eclipse about which Tomcat we are using and set up the integration.
2.From the menu bar select Window->Preferences.
3.The Preferences window will open. Expand Server.
4.Highlight Runtime Environment. This is the place where you can tell Eclipse about where you put your Tomcat installation.
5.Click Add.
6.Expand Apache and select Apache Tomcat v6.0.
7.Check the Create a new local server check box to create a new server in the Servers view.
8.Click Next.
9.Leave the Name of the server set to Apache Tomcat v6.0.
10.Eclipse gives the option to download a version of Tomcat but it usually does not have the latest version (which is why we downloaded it separately). Click Browse and navigate to c:\java\tomcat and click Ok.
11.Leave the JRE drop down set to Workbench default JRE.
12.Click Finish.
13.You are taken back to the Server Runtime Environments preference page so click Ok.
14.A new project will have been created and if you go into the Servers view (in the bottom set of tabs), you will see a new server Apache Tomcat v6.0 at localhost.

Create project
1.There are several different types of project in Eclipse and we need the one that will allow us to integrate all the things we need.
2.Select File->New->Dynamic Web Project
3.Enter a Project name. Although you can have spaces, in my opinion, it’s best not to put any in. The project name becomes the directory name and for the same reason as above it’s a pain if there are spaces.
4.The Target Runtime should already be set to Apache Tomcat v6.0.
5.Also keep the Configuration set to Default Configuration for Apache Tomcat v6.0.
6.Click Finish.
7.In the Project Explorer, right click on the new project and select Spring Tools->Add Spring Project Nature.

Spring Web project and Tomcat project association
1.We must now associate the project with Tomcat.
2.Make sure the Servers view is visible (in the bottom set of tabs). Highlight your new Spring Web project and drag it on to the Tomcat v6.0 Server at localhost entry in the Servers tab.
3.We want to use the Tomcat server when we use our new project, so we can set the Server project to be a dependency of our new project. This will mean that when we open our project the Server project will open automatically.
4.Right click on our project and select Properties.
5.Select the Project References option and check the Servers project.
6.Click Ok.