Java-Rules: 01/01/2012

Wednesday, January 25, 2012

arithmetic operators

//arthemetic operators using switch

import java.io.*;

class Input2

{

public static void main(String[] args)throws IOException

{

char ch;

InputStreamReader ir=new InputStreamReader(System.in);

BufferedReader br=new BufferedReader(ir);

System.out.println("enter values of x");

int x=Integer.parseInt(br.readLine());

System.out.println("enter values of y");

int y=Integer.parseInt(br.readLine());

System.out.println("enter u r choice");

System.out.println("+ for additon");

System.out.println("- for subtraction");

System.out.println("/ for divide");

System.out.println("* for multipiy");

System.out.println("% for remainder");

ch=(char)br.read();

switch(ch)

{

case '+':

System.out.println("additon:"+(x+y));

break;

case '-':

System.out.println("sub:"+(x-y));

break;

case '*':

System.out.println("mul:"+(x*y));

break;

case '/':

System.out.println("divide:"+(x/y));

break;

case '%':

System.out.println("Remainder:"+(x%y));

break;

}

Reading an integer from keyboard

// input from key board

import java.io.*;

class Inputint

{

public static void main(String r[])throws IOException

{

InputStreamReader id=new InputStreamReader(System.in);

BufferedReader br=new BufferedReader(id);

System.out.println("enter a interger");

int s=Integer.parseInt(br.readLine());

System.out.println("enter "+s);

}

reading a string from keyboard

// input from key board
import java.io.*;
class Inputstring
{
public static void main(String r[])throws IOException
{
//InputStreamReader id=new InputStreamReader(System.in);
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("enter a String vslue");
String s=br.readLine();
System.out.println("enter "+s);
}
}

Simple AJAX Program

Simple AJAX application using java script and JSP.

Files required.

1. ajax.js
2. mainpage.jsp
3. process.jsp
4. web.xml

Code :

1. ajax.js

var xmlHttp;
function postRequest(url) {

if (window.XMLHttpRequest) { // Mozilla, Safari, ...
//alert("other than IE");
xmlHttp = new XMLHttpRequest();

} else if (window.ActiveXObject) { // IE
//alert("IE only");
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");

}

xmlHttp.open('POST', url, true);
xmlHttp.onreadystatechange = function() {

if (xmlHttp.readyState == 4) {
updatepage(xmlHttp.responseText);

}

}

xmlHttp.send(url);

}

function updatepage(str){

document.getElementById("result").innerHTML = "<font color='green' size='15'>" + str + "</font>";

}

function showCurrentTime(){

var url="process.jsp";
postRequest(url);

}

2. mainpage.jsp

<%@ page import="java.util.*" %>
<html>
<head>

<title>Ajax Example</title>
<script type="text/javascript" src="ajax.js"> </script>
</head>

<body>

<h1 align="center"><font color="#000080">Ajax Example</font></h1>
<%
out.println(new Date());
%>
<p><font color="#000080"> This very simple Ajax Example retrieves the
current date and time from server and shows on the form. To view the current
date and time click on the following button.</font></p>

<form name="f1">

<p align="center"><font color="#000080"> <input value=" Show Time "
type="button" onclick='JavaScript:showCurrentTime()' name="showdate"></font></p>
<div id="result" align="center"></div>

</form>
<div id=result></div>
</body>

</html>

3. process.jsp

<%@ page import="java.util.*" %>
<%
out.println(new Date());
%>

4. web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>AjaxApp1</display-name>

<welcome-file-list>
<welcome-file>mainpage.jsp</welcome-file>

</welcome-file-list>
</web-app>

Simple AJAX program with struts 1.2

Files required :

1. ajax.js
2. search.jsp
3. web.xml
4. struts-config.xml
5. SearchForm.java
6. SearchAction.java

Code for running the program :

1. ajax.js

var request;

function createObject() {

if (window.XMLHttpRequest) { // Mozilla, Safari, ...

//alert("other than IE");

request = new XMLHttpRequest();

} else if (window.ActiveXObject) { // IE

//alert("IE only");

request = new ActiveXObject("Microsoft.XMLHTTP");

}

function search() {

createObject();

var name=window.document.getElementById("n").value;

var url="search.do?name="+name;

request.open('GET',url,true);

request.send(url);

request.onreadystatechange= callback();

}

function callback() {

if (request.readyState == 4) {

displayInfo(request.responseText);

}

function displayInfo(str) {

/*This function is only for testing, not working*/

}

2. search.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ page import="java.util.*" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Search Page</title>
<script type="text/javascript" src="ajax.js">
</script>
</head>
<body>
<table>
<form action="search.do">
<tr>
<td>Enter name Here : </td>
<td><input id="n" type="test" name="name" onkeyup="search()"/></td>
</tr>
<div id="results"></div>
</form>
</table>
</body>
</html>

3. web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.5" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<display-name />
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>search.jsp</welcome-file>
</welcome-file-list>

</web-app>

4. struts-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN" "http://struts.apache.org/dtds/struts-config_1_2.dtd">

<struts-config>
<form-beans>
<form-bean name="searchForm" type="com.search.SerachForm"></form-bean>
</form-beans>
<action-mappings>
<action path="/search" name="searchForm" type="com.search.SearchAction">
<forward name="success" path="/search.jsp"></forward>
</action>
</action-mappings>
</struts-config>

5. SearchForm.java

package com.search;

import org.apache.struts.action.ActionForm;

public class SerachForm extends ActionForm {
private String name;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

6. SearchAction.java

package com.search;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

public class SearchAction extends Action{
/*
* author : Chandrasekhara Kota
* Date : 03-Dec-2011
* Email : chandunaidu.kota@gmail.com
* */

public ActionForward execute(ActionMapping am, ActionForm af, HttpServletRequest req, HttpServletResponse res)throws Exception
{
System.out.println("---------------inside the action------------------"+req.getParameter("name"));

return am.findForward("success");
}
}

Monday, January 23, 2012

static variable

/*
static most powerful and beautiful concept in java .if use static, jvm will load at the time of class load.
if we use static for a variable it treated as class level variable for every new object will not create new variable existing only used.
*/

public class Static_Variable
{
static String collegename="ghandi college";
public void method1()
{
//incomplete
}
}

static NOT applicable with modifiers

/*
RULE: static keyword not applicable with the
1.final
2. abstract
and class

*/

static applicable

/*
RULE: static keyword only applicable for variables , methods and block but not for classes
*/

public class Static_Demo
{
static int x=10;
static
{
System.out.println(x);
}
public static void main(String arg[])
{
System.out.println("static main method")
}
}

public class

/*
RULE: if we declared a class as public, we can access that class from any where
*/

public class Public_Class
{

}

protected class

/*
RULE: a class declared as protected, than it can be visible or access in the child classes of the same package and out side of the child classes
*/

protected class Protected_Class
{

}

default class

/*
RULE: if not declared a with public or protected, it treated as default class. a default class can access with in the package of the child classes but not out side of the package.
*/

package com.default.pack;
class Default_Class
{

}

package com.default.pack;
import com.default.pack;
class Default_Class_Use
{
Default_Class dc=new Default_Class();
}

//

package com.other.pack;
import com.default.pack;
class Default_Class_Use
{
Default_Class dc=new Default_Class(); //compile time error
}

abstract class

/*
RULE: we can declare a class as abstract, if we declare a class as abstract that means all the methods in that class need not be abstract. that abstract class may be not with abstract methods or normal methods
*/

public abstract class Abstract_Class
{
abstract method1();
abstract method2();
public void method3()
{
System.out.println("normal method");
}
}

Demo 2:

public abstract class Empty_Abstract
{

}

in final class

/*
RULE: if we declared a class as final that means in that class all the methods are by default final but variables are not final
And it can not support the inheritance concept. and run time polymorphism But it can support the static polymorphism
*/

public final class Final_Class
{
int x=10;
public void method1()
{
System.out.println(x);
x=20;
System.out.println(x);
}
public void method1(int x)
{
this.x=x;
System.out.println(x);
}
}
class Demo extends Final_Class
{
public void method1()
{
System.out.println("child");
}
}

class can applicable with modifiers

/*
RULE: class can applicable with the following modifiers are
1.public
2.final
3.abstract

*/

class canNOT applicable modifiers are

/*
RULE: class canNOT applicable with the following modifiers are
1.private
2.protected
3.strictfp (only for methods)
4.synchronized (only for methods/blocks)
5.native (only for methods)
6.volatile (only for variables)
7. transient (only for variables)
8.static (only for methods/variables/blocks)

*/

class

/*
RULE : class is keyword by using class keyword we can achieve the encapsulation mechanism
in oops.
Definition: class is an way of creating user defined data types.
*/

class Class_Structure
{
static variables;
.
.
instance variables;
.
.
{
//instance block
}
static
{
//static block
}
methods()
{
}
}

final NOT applicable 4

/*
RULE: final key word not applicable for the following modifiers only
1.abstract
2.
3

in complete
*/

final applicable 4 only

/*
RULE: final key word applicable for the following modifiers only
1.public
2.private
3.protected
4.<<default>>
5.native
6.static
7.
in complete
*/

final variable

/*
RULE: we can declare a variable as final and not necessary declare a variable until it will be use.
we can initialize the variable at the time of use it.
*/

public class Final_Variable
{
public static void main(String ar[])
{
final int x;
System.out.println("hello"); //no error its legal
x=10;
System.out.println(x);
}
}

final instance variable

/*
RULE: we can declare instance variable as final but jvm wont provide any default values for instance variable, programmer have provide the values for final instance variables .
we can provide values in three ways
1. at the time of declaring the variable.
2. in constructor.
3.in instance block
*/

public class Final_Instance_Variable
{
final double d;
public static void main(String ar[])
{
System.out.println(x); // compile time error
}
}

Way 1 : initialization value for final instance variable

public class Final_Instance_Variable
{
final double d=20.3;
public static void main(String ar[])
{
System.out.println(x);
}
}

Way 2 : initialization value for final instance variable

public class Final_Instance_Variable
{
final double d;
public Final_Instance_Variable()
{
d=20.3;
}
public static void main(String ar[])
{
System.out.println(x);
}
}

Way 3 : initialization value for final instance variable

public class Final_Instance_Variable
{
final double d;
{
d=20.3;
}
public static void main(String ar[])
{
System.out.println(x);
}
}

Final Static Variable

/*
RULE: we can declare a static variable as final , but jvm not provide any default values for final static variables
we have to provide before class load. we can provide in two ways in static block or by the time of declaring the variable.
*/

public class Final_Static_Variable
{
final static int x;
public static void main(String ar[])
{
System.out.println(x); //error
}
}

Demo For Initialization for static final variable.(way 1)

public class Final_Static_Variable
{
final static int x=10;
public static void main(String ar[])
{
System.out.println(x); //error
}
}

Demo For Initialization for static final variable.(way 2)

public class Final_Static_Variable
{
final static int x;
static{
x=10;
}
public static void main(String ar[])
{
System.out.println(x); //error
}
}

abstract applicable for what

/*
RULE: abstract key word only applicable for CLASSES and METHODS not for variables
*/
public abstract class AbstractDemo
{
abstract int x; // illegal
abstract public void method1();
abstract public int method2();
}

Spring

Wednesday, January 25, 2012

Simple AJAX Program

Simple AJAX program with struts 1.2

Monday, January 23, 2012