static-a key word

Lets explain that what is static  in java.

if we make a class static then it means members of this class will be accessed directily by class name.and we can not create instanse of this class.

only static mamber can access to other static member.
 if any non-static member want to access any non-static member then it need to access throught the instance of that class
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Custom Exception

Defining your own Exception class in JAVA
Now you know how to write exception handlers for those exception objects that are thrown by the runtime system, and thrown by a method in the standard class library.
It is also possible for you to define your own exception classes and to cause objects of those classes to be thrown whenever an exception occur. In this case, you get to decide just what constitutes an exceptional condition. For example, suppose you could write a data-processing application that processes integer data obtained via a TCP/IP link from another computer. If the specification for the program indicates that the integer value 100 should never be received, then you could use an occurrence of the integer value 100 to cause an exception object of your own design to be thrown.

 exceptFig1.jpg.gif
Exception Types

Mainly Exceptions are of two types; checked and unchecked exceptions:
  • Error and Runtime Exception are unchecked these exception not handled or check by compiler that you  handle them explicitly
  • All other Exception are checked that is compiler enforce or check that you can handle them explicitly
An error is an abnormal situation of the JVM (Java Virtual Machine)
  • Running out of memory
  • Infinite recursion
  • Inability to link
Creating Custom Exceptions
  • Use the Exception class in the API.
  • Create a Custom Exception class if  the predefined class is not sufficient.
  • Declare a custom exception classes by extending the Exception class or  a subclass of Exception.
If you decide to define your own exception class. it must be a subclass of a Throwable class. You must decide which class you will extend.
The two existing subclasses of Throwable are Exception and Error.   Example-1 
This example is making your own Exception class by using constructor. 

// this is a user define exception class etend by Exception class
class Myexception extends Exception
     {
      public Myexception(int i)
        {
        System.out.println("you " +i +" entered It exceeding the limit");
        }

      }

public class ExceptionTest
    {
    public void show(int i) throws Myexception
          {
       if(i>100)
         throw new Myexception(i);
       else
         System.out.println(+i+" is less then 100 it is ok");
          }

   public static void main(String []args)
        {
        int i=Integer.parseInt(args[0]);
        int j=Integer.parseInt(args[1]);
        ExceptionTest t=new ExceptionTest();
            try{
                t.show(i);
                t.show(j);
                }
                catch(Throwable e)
                        {
                System.out.println("catched exception is"+e);
                        }
        }
}
OUTPUT
customexception cmd.gif
Example-2
This example is making your own Exception class by using super keyword.
class MyException extends Exception
    {
    MyException(String s)
     {
      super(s);
     }
    public String toString()
        {
           return(" " + getMessage());
        }
   }class ThrowClass  {
    int age;
     ThrowClass(int age)  throws MyException
       {
       this.age=age;
       }        
     void getAge(int age) throws MyException
      {
       if(age <18 )
        {
         throw new MyException("Invalid Age");
              }
        else
        {
         this.age=age;
        }
      }
   }
   class TestException   {
    public static void main(String [] args)
     {
        int a=Integer.parseInt(args[0]);
       try        {
          ThrowClass t=new ThrowClass(a);
            t.getAge(a);
       System.out.println(t.age);
        }
        catch(MyException me)
           {
          System.out.println(me);
              }
     }
   }
OUTPUT
testException.gif 
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Aggregate Functions:



 They are used to compute a single value from a set  of attribute values of a column:
   count :
            how many rows(tuples) are stored in the relation EMP
select count(*) from EMP;
            how many different job title  are stored in the relation EMP
select count(distinct job) from EMP;
max & min:
           select min(SAL),max(SAL) from EMP
           select max(SAL)- min(SAL)  from EMP
sum:
         select sum(SAL) from EMP
avg:





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PL/SQL



Structure of PL/SQL:
     Declare
              <Constants>
               <Variables>
               <Cursors>
                <User defined exceptions>
Begin
         <PL/SQL Statements>
          exception
               <exception handling>
End

Know in PL/SQL:
About
1.Exception handling
2.Procedures
3.Functions
4.assertions
5.Triggers

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Tags



<abbr> Tag

The <abbr> tag is supported in all major browsers.
<abbr title="World Health Organization">WHO</abbr>
Note: The <abbr> tag is not supported in IE 6 or earlier versions.
Tip: The global title attribute can be used in the <abbr> tag to show the full version of the abbreviation/acronym when you mouse over the <abbr> element.
<acronym>  Tag
<acronym title="as soon as possible">ASAP</acronym>

<bdo> Tag

<bdo dir="rtl">
This text will go right-to-left.
</bdo>

<caption> Tag

<table border="1">
  <caption>Monthly savings</caption>
  <tr>
    <th>Month</th>
    <th>Savings</th>
  </tr>
  <tr>
    <td>January</td>
    <td>$100</td>
  </tr>
</table>
The <caption> tag defines a table caption.

<col> Tag

table border="1">
  <colgroup>
    <col span="2" style="background-color:red">
    <col style="background-color:yellow">
  </colgroup>
  <tr>
    <th>ISBN</th>
    <th>Title</th>
    <th>Price</th>
  </tr>
  <tr>
    <td>3476896</td>
    <td>My first HTML</td>
    <td>$53</td>
  </tr>
</table

<del> Tag

<p>My favorite color is <del>blue</del> <ins>red</ins>!</p>

<fieldset> Tag

<!DOCTYPE html>
<html>
<body>
<form>
 <fieldset>
  <legend>Personalia:</legend>
  Name: <input type="text"><br>
  Email: <input type="text"><br>
  Date of birth: <input type="text">
 </fieldset>
</form>
</body>
</html>

<hr> Tag

<!DOCTYPE html>
<html>
<body>

<h1>HTML</h1>
<p>HTML is a language for describing web pages.</p>

<hr>

<h1>CSS</h1>
<p>CSS defines how to display HTML elements.</p>

</body>
</html>

<mark> Tag

<!DOCTYPE html>
<html>
<body>

<p>Do not forget to buy <mark>milk</mark> today.</p>

</body>
</html>

<meter> Tag

<!DOCTYPE html>
<html>
<body>

<p>Display a gauge:</p>
<meter value="2" min="0" max="10">2 out of 10</meter><br>
<meter value="0.6">60%</meter>

<p><b>Note:</b> The &lt;meter&gt; tag is not supported in IE and Safari.</p>

</body>
</html>

<nav> Tag

<!DOCTYPE html>
<html>
<body>

<nav>
<a href="/html/">HTML</a> |
<a href="/css/">CSS</a> |
<a href="/js/">JavaScript</a> |
<a href="/jquery/">jQuery</a>
</nav>

</body>
</html>

<optgroup> Tag

<!DOCTYPE html>
<html>
<body>

<select>
  <optgroup label="Swedish Cars">
    <option value="volvo">Volvo</option>
    <option value="saab">Saab</option>
  </optgroup>
  <optgroup label="German Cars">
    <option value="mercedes">Mercedes</option>
    <option value="audi">Audi</option>
  </optgroup>
</select>

</body>
</html>

<param> Tag

<!DOCTYPE html>
<html>
<body>

<p><b>Note:</b> IE does not support .wav files. Try to rename the file to "horse.mp3" to test the example in IE.</p>

<object data="horse.wav">
<param name="autoplay" value="true">
</object>

</body>
</html>

<pre> Tag

<!DOCTYPE html>
<html>
<body>

<p><b>Note:</b> IE does not support .wav files. Try to rename the file to "horse.mp3" to test the example in IE.</p>

<object data="horse.wav">
<param name="autoplay" value="true">
</object>

</body>
</html>

<progress> Tag

<!DOCTYPE html>
<html>
<body>

Downloading progress:
<progress value="50" max="100">
</progress>

<p><b>Note:</b> The &lt;progress&gt; tag is not supported in IE and Safari.</p>

</body>
</html>

<s> Tag

<!DOCTYPE html>
<html>
<body>

<p><s>My car is blue.</s></p>
<p>My new car is silver.</p>

</body>
</html>

<strike>

<!DOCTYPE html>
<html>
<body>

<p>Version 2.0 is <strike>not yet available!</strike> now available!</p>

</body>
</html>

<sub> and <sup> Tags

<!DOCTYPE html>
<html>
<body>

<p>This text contains <sub>subscript</sub> text.</p>
<p>This text contains <sup>superscript</sup> text.</p>

</body>
</html>



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OSI Model

Open System Interconnection Model:
Physical Layer:
it performs all the functions related for establishing a physical home of communication
like hardware specification,topology,encoding n signaling etc.

Data Link Layer:
it provides the reliable transmission of a packet using physical layer services.Means it links the data to physical layer.
it is also dived into two parts Medium acces layer and Logical Link layer

Network Layer:
It provides the way of transmission of packets(routing) n also congestion control n internetworking.

Transport Layer:
it performs the transmission of packets like using Multiplexing/demultiplexing,fregmentation,error control,flow control etc.

Session Layer:
It is responsible for all the authorization security by creating sessions.

Presentation Layer:
It tells us that in which syntax n semantics  the informations should be transmitted n also include compression,encryption.

Application Layer:
Application layer refers to Application Protocol.The choice of which specific protocol n thier associated functions r to be used at the application lavel is up to the individual user HTTP,FTP etc.
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Codes

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Class javax.servlet.http.HttpServlet

javax.servlet.GenericServlet | 
+----javax.servlet.http.HttpServlet
public abstract class HttpServlet
extends GenericServlet
An abstract class that simplifies writing HTTP servlets. It extends the GenericServlet base class and provides an framework for handling the HTTP protocol. Because it is an abstract class, servlet writers must subclass it and override at least one method. The methods normally overridden are:
  • doGet, if HTTP GET requests are supported. Overriding the doGet method automatically also provides support for the HEAD and conditional GET operations. Where practical, the getLastModified method should also be overridden, to facilitate caching the HTTP response data. This improves performance by enabling smarter conditional GET support.
  • doPost, if HTTP POST requests are supported.
  • doPut, if HTTP PUT requests are supported.
  • doDelete, if HTTP DELETE requests are supported.
  • The lifecycle methods init and destroy, if the servlet writer needs to manage resources that are held for the lifetime of the servlet. Servlets that do not manage resources do not need to specialize these methods.
  • getServletInfo, to provide descriptive information through a service's administrative interfaces.
Notice that the service method is not typically overridden. The service method, as provided, supports standard HTTP requests by dispatching them to appropriate methods, such as the methods listed above that have the prefix "do". In addition, the service method also supports the HTTP 1.1 protocol's TRACE and OPTIONS methods by dispatching to the doTrace and doOptions methods. The doTrace and doOptions methods are not typically overridden.
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JSP Element Type

Directive:
<%@   %>
e.g
page directive 
<%@ page import=”abc.* session=””false”   %>
A page directive can use up thirteen different attributes
        1.  import
        2. isTheadsafe
        3. contentType
        4. isELIgnored
        5. isErrorPage
        6. errorpage
        7. language
        8. extends
        9. session
       10.buffer
       11. autoFlush
       12. info
       13. pageEncoding
taglib directive
<%@ taglib tagdir=”/WEB-INF/tags/krrish prefix=””krrish” %>
include directive
<%@ include file=”krrish.html” %>
Declaration:
             <%!     %>
Scriptlet:
            <%    %>
Expression:
          <%=     %>
EL Expression:
            $(   )
e.g
email:$(application.mail)
Action:
Standard  action
<jsp:include  page=”abc.jsp”>abc</jsp>
e.g

  • jsp:include 
  • jsp:param
  • jsp:forward
  • jsp:plugin
  • jsp:fallback
  • jsp:getProperty  
  • jsp:setProperty
  • jsp:useBean
Other action
<c:set var=”rate” value=”32”/>
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