Confusion in line

Question

Hi,
I really don't understand the following line from Head First book page no. 362:
Watch what happens if you make ALL the request parameter names match the bean property names. The person bean(which is an instance of foo.Employee) actually has two properties----name and empID.
In the above line person is declared as an attribute in request scope in Servlet with object foo.Employee, and it is called in JSP standard action with the id="person" in <jsp:useBean> tag. So, it is clear the Tomcat will convert the person attribute as:
foo.Employee person=new foo.Employee();
As from the Java perspective, instance and object are synonym. So, why it is called an instance a reference instead of Object?
Edited by: Hunky322 on 22 Jun, 2009 4:54 PM

Answer 1

Hunky322 wrote:
In the above line person is declared as an attribute in request scope in Servlet with object foo.Employee, and it is called in JSP standard action with the id="person" in <jsp:useBean> tag.Not quite correct. 'foo.Employee' is a Java class. Unfortunately, quite a lot of documentation makes this mistake.
So, it is clear the Tomcat will convert the person attribute as:
foo.Employee person=new foo.Employee();yup
As from the Java perspective, instance and object are synonym.Hmmm...OK, an object is an instance of a Java class.
So, why it is called an instance a reference instead of Object?Watch your capitalization: 'Object' and 'object' are not the same thing.
But, to answer your question: because all objects are stored by their reference (an internal pointer to the piece of memory that holds the constructed object). However, unlike languages like C and C++, you do not have access to this value as anything other than an accessor to the instance itself. There is no such thing as "pointer arithmetic" in Java.
HIH
Winston