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What is the default value of an object reference declared as an instance variable?

+3 votes
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What is the default value of an object reference declared as an instance variable?
posted Jul 15, 2015 by Karthick.c

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1 Answer

+1 vote

null unless we define it explicitly.

answer Mar 22, 2016 by Shivam Kumar Pandey
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+2 votes

I declared a variable and incremented/modified it inside Mapper class. Now I need to use the modified value of that variable in Driver class. I declared a static variable inside Mapper class and its modified value works in Driver class when I run the code in Eclipse IDE. But after creating that code as a runable jar from Eclipse and run jar file as “$ hadoop jar filename.jar input output” modified value does not reflect (value is 0) in Driver class.

+2 votes
public class ServletClassName extends HttpServlet {
//declare instance variables for the servlet
int  instanceVar ; // not thread−safe
// overriding the Generic Servlet.init ( )
@Override
public void init ( ) throws ServletException {
// initialize instance variables, etc.
instanceVar = 0 ;
}
. . .
}

Per each page request, in the service() method (which eventually will be either doGet(), doPost(), or whatever),
you can manipulate instance variables.

Write a Servlet that counts the total number of visits (how many times it's being visited from all clients). The Servlet should display the following information

• Total Page Visits:
• Client Remote Address:
• Client Host Address: <client_fully_qualied_url__or__client_IP_address>

The last two can be obtained from the HttpServletRequest, Refer to the Java EE API

then how can re-do these using the Java API for HttpSession.

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