Advanced Java Questions and Answers

1 :: What we can not do in jdbc but can do hibernate?

There are many thing we can do in hinernate automaticaly by
hibernate tools or seting hibernate properties.some I
giving below:
(1) We can migrate database just change database dielect.
(2)we can used caching
(3)if user do not know ant any SQL languge then they can
use criteria query.
(4)There is one scnerio where SQL query are failed when
want fetch obejct from db but do not know there ID.
Hibernate provide this solution using HSQL.

2 :: Java is fully object oriented languages or not? Why?

No,java is not fully object oriented language because it does not support "multiple inheritence" and "pointers" which are used in C++.But,by using Interfaces we can implement multiple inheritence.Also,due to presence of Primitive datatypes,which are used in (AutoBoxing)...we can say it is not fully object oriented language.

3 :: If i learn Java, what kind of applications can i create that will help Banking, Retail, Hotel, Logistics industry?

When learned the java with the advanced concepts ,the
application can be created for all the domain.Using the
J2EE will be more friendly and efficiency in the code
maintenance, since part of the code will be from the
framework

4 :: What is difference between object state and behavior?

If you change the state of an object, you ask it to perform
a behavior. An object stores its states in a field e.g.
variables, and demonstrates its behavior through methods.

5 :: Can we have more than one action servlet?

yes you can have and if you specify different url patter
like
*.do for one action servlet
*.abc for other action servlet
in your web.xml file

6 :: Why use a datasource when you can directly specify a connection details? (in a J2EE application)?

Because, it would be really difficult to specify the connection details in every method that access the database. Instead, if we create a data source, it can be used to connect to the database in every method we want.

7 :: If I define a method in JSP scriplet <%..%>, where will it go after translation into a servlet?

It will give compilation error. In order to define a method
in JSP, it should be defined in the JSP declarations <%!..%
>, and it can be called in the JSP expression.
On translation, the method will be added outside all
methods in the servlet class.

8 :: How will the struts know which action class to call when you submit a form?

struts-config.xml in this file.
under the tag <type> absolute path of Action class
under the tag <name> name of the action form class
Both of this will be called when the desired action
mentioned under the <path> tag will be called and
struts-config.xml will call action class mentioned in the
<type> tag and also populate the fields of form class
mentioned under <name> tag.

9 :: Will it be called overriding if I do not change the parameters or return type, instead throw a different exception in the method signature?

yes, you will be overriding to throw a different exception

10 :: Does Java pass arguments by value or reference?

Pass by value.
1. When passing primitives, it passes a copy of the
variable to the method. Any change made in the method does
not reflect in the calling method.
2. When dealing with objects, a copy of their
reference/address is passed. Thus the change made to the
object is reflected in the calling method.

11 :: Different between Struts and Spring? or Why use Spring, if you are already using Struts?

Struts:
1.Struts is only for web Applications.We can not develop any
type of Java,J2EE applications by using Struts Framework.
2.We can not Integrate other Frameworks with Any other Java
Oriented Frameworks.
Spring:
1.Spring is for developing any kind of Java,J2EE applications.
2.It is Layered architecture.We can integrate any no of
Frameworks with Spring.
3.It has So many features like AOP,IOC.

12 :: Explain what is synchronization?

When multiple threads working,Synchronization is to lock a method for a particular object.

13 :: Write a program to show synchronization?

public someClass{
public synchronised methodA(){
//write your code
}
}

14 :: Explain what is orm?

Object Relational Mapping ,its a tool for transaction management that needs to be integrated with Spring,Struts etc.Eg : Hibernate,iBatis,JDO etc

15 :: Write a singleton program?

Having single instance through out the application.eg.: Loggers

16 :: What is IOC concept & explain it?

Injecting dependencies to object itself instead of depending on container.

17 :: Explain spring framework?

Spring is lightweight,Inversion controlled,Aspect oriented ,Container framework.

18 :: What are the oops concept?

Inhertitance, Encapsulation, Polymorphism, Data Abstraction

19 :: What are the diff types of exception?

Unchecked and Checked exceptions

20 :: What is AOP(assepct oriented programing)?

Separating your business logic with other functionalit
y such as services,Loggers etc,Making classess more cohesive.

21 :: What is jsp life cycle?

jspinit(),_jspService(),jspdestroy()

22 :: Explain servlet life cycle?

init(),service(),destroy()

23 :: What is prototype?

Having multiple instances or having clones

24 :: In spring bean class uses singleton or prototype?

By Default spring uses singleton or mention singleton="true" for singleton else false for prototype inside bean tag.