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SCJP Notes - Part 8

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1) Static blocks/static methos/static variables are executed first in the order of thier appearance in the code.
After executing static's instance blocks/instance methos/instance variables are executed.
2) The reference may be null when calling a static method from main method.
3) float arr[][] = new float[][10]; is wrong
float arr[][]...
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SCJP Notes - Part 7

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1) The final keyword on a method means that the method cannot be overridden in a subclass. But since the main() method is a static method, it can't be overridden anyway. So making the main() method final makes no sense.

2) main method can be final.

3) A class without a main method can be run by JVM, if its ancestor class has a main method....
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SCJP Notes - Part 1

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...
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JSP usebeans facts

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1<jsp:getProperty name="test" property="date"/> will print the value of property.

2<jsp:useBean id="test" class="com.Example">
<jsp:setProperty name="test" property="*"/>
</jsp:useBean>

3 <jsp:setProperty name="test" property="date"...
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JSP implicit objects

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request javax.servlet.http.HttpServletRequest
response javax.servlet.http.HttpServletResponse
pageContext javax.servlet.jsp.PageContext
page java.lang.Object
config javax.servlet.ServletConfig
out ...
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Resend Information on page refresh

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The message when refreshing a page is displayed when session is being used by the JSP/Servlet.

In Servlet, session is got by:
HttpSession session = request.getSession(true);


In JSP the way is:
<% page session="true"%>



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Directives as tags

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Alternative tags for directives
<jsp:directive.page import="java.util.*" />


instead of
<%@ page import="java.util.*" %>


The use of tags helps in better compatibility with JSTL and custom tags
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Work that can be done with request and response

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request--
1 getParameter
2 cookies
3 request method (GET/POST)
4 getSession

response--
1 setParameter
2 getWriter
3 setContentType
4 addCookie

out in JSP refers to buffered version of PrintWriter which is known as JSPWriter
session has getAttribute("name") and setAttribute("name","value")
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The HTML you thought to be present in your JSP

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Consider the code below:

...
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Use Encoded URL in the form tag in JSP

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<% String url = response.encodeURL("Myjsp.jsp"); %>

<form method="post" action=<% url %>?param=value")
</form>


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Compiler error for unreachable code

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A sample:

while ( false ) {	System.out.println ( "Value" );}while(3>4) {	System.out.println ( "Value" );}
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Prototype Pattern

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The prototype pattern is used in cases where the cost of creating a new object is much more than simply editing the attributes of an already existing object. So this pattern should be used when one has the privileges to modify the desired attributes of the object.
In java, the prototype of an object can be got by using the clone method. The method...
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Object Pool

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Connection pooling is the process of maintaining a pool of connection and reusing them each time some statement is to be executed in the database. It is a general concept which can be applied in any programming language, but here we will implement it in Java programming language.

Design:
A class will maintain all the connections in a vector...
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Singleton Pattern

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The Singleton pattern is used for classes which should have only one instance in the application. The other classes can't invoke the constructor directly because it is declared private and some public static method is provided which returns the single instance. This pattern makes the instance available globaly and thus should be used...

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