Interview Java J2EE Questions and Answers - Question and answer on various Technologies

Main .............. Technical Interview Questions, answers, Core Java, FAQ.

Some of the Core Java Interview questions with answer as listed below:
If any of the questions ans answer, you find not upto expectation,
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Java Question
How to handle / centrailize exception handling strategy in a Swing based application?

J2EE Interview Question
What will happen if exception occurs in a Tag Library Java class? Where will it be propagated
or caught?

J2EE Interview answer
No answer found yet.

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Java Interview question
How can you describe Visitor Design pattern with a real world case?

No answer found yet.
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Java Interview question
What are the basic difference between using ArrayList and LinkedList as a high volume data insertion,
deletion and updation activities?

ArrayList has a default initial size, and when maximum capacity of this ArrayList is reached, then
an array copy to another array happens, and on removal of any element from array list will result
in array reshuffling, thus could impact performace.

In case of Linked List, all the elements are having a link mentioned in another internal element/node list.
Thus in case of removal of an element from linked list, will result in simply the link of previous
element pointing to the next element now, so performance can be comparatively better, if number / size
of linked list is big.

Java Interview question
Can there be a datastructure that has all benifits of ArrayList and LinkedList, like faster
get/retrieve operation and faster removal of elements from list ?

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Core Java Interview Questions with answer


Java Interview question 1 
What is immutable in Java Technology? 
Java Interview answer 
String is immutable. 

Java Interview question 2
What is the difference does it have over other objects? 

Java Interview answer 
Immutable object like String, whose value once initialized
 can never be changed, that is when object or instance of 
String is created and initialized, then the reference of 
this object points to a value that can never be changed. 

Java Interview question 3 
Can a private variable be also declared as final? If yes,
why and if no, why? 

Java Interview answer 
I think, No, one can not define a private variable as final, as a
private variable can not be visible outside this class,

so there is no need for a private variable to be defined as final.




Java Interview question  
What will happen if I try to compile a Java program
at runtime by using another Java program?
How could I create , compile and load a Java class
file from another Java program?
Basically I am trying to create an IDE (development environment)
where by I should be generating Java code based on some
user input and compiling and running this program
by click of a menu from IDE?

Java Interview answer
You can explore using Castor or any other Framework
for dynamic class file generation and then can
use Runtime api to compile and system class loader
api to load this class into the JRE of the IDE
to be able to run the generated class file.

Java Interview question  
What is Generalization (UML) in Java Code perspective?

It is a Java class extending to another Java class or
the inheritance principle.

Java Interview question  
What is Realization (UML) in Java Code perspective?

It is a Java class implementing an interface or actually
realizing an interface in a Java class.

Java Interview question  
What is Association(UML) in Java Code perspective?

It is when a Java class has any other Java class as variable
and it is using the other class.

Java Interview question  
What is Composition(UML) in Java Code perspective?

It is when a Java class C1 has any other Java class C2 as variable
and it is creating an instance of C2 class in it. So when object of
C1 is set to null or dies , so object/instance of C2 dies too.

Java Interview question  
What is Aggregation (UML) in Java Code perspective?

It is when a Java class C1 has collection of any other Java class 
instance as variable and this collection is populated by some other
object, so C1 doesn't control life cycle of these objects in collection.

please correct me if I am wrong in answering any of these question,
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