1. What are Web Services?
Web
services are business logic components which provide functionality via. Internet
using standard protocols such as HTTP. It is created using Soap or Rest. For
E.g. in google search page we got results like feeds, advertisement , news
etc., from multiple sites, it is by web services
which enables various websites to talk to each other and share data between
them.
2.
Differences between Soap vs. Rest.
SOAP -
"Simple Object Access Protocol"
·
SOAP is a method of transferring messages, or small amounts of
information, over the Internet. SOAP messages are formatted in XML and are
typically sent using HTTP (hypertext transfer protocol).
Rest -
Representational state transfer
·
Rest is a simple way of sending and receiving data between client
and server and it doesn't have very many standards defined. You can send and
receive data as JSON, XML or even plain text. Its light weighted compared to
SOAP.
3.
How to create a DB connection.
Five
steps to query a database:
1.
Load the driver
2.
Get connection
3.
Query the database
4.
Process the result set
5.
Close connection
4.
Differences between prepared statement and callable statement.
Prepared
Statement – Execute a precompiled SQL with/without input parameters.
Callable
Statements – Execute a call to database stored procedure.
5.
Difference between Application server and Web server.
Application server
|
Web server
|
Web server serves HTTP content
|
Application server serves HTTP, RMI/RPC etc.
|
Webserver is suitable for static content.
|
Application server supports dynamic content also.
|
Webserver does not contain inbuilt web server component.
|
Application server contains inbuilt web server component.
|
IIS, Jetty, Tomcat, Apache etc... Is webserver
|
SharePoint, JBOSS, EJB, WAS etc… Is application server.
|
Webserver does not add any functionality
|
Application server adds functionality
To applications.
|
6.
Difference between System. Out and System. Err.
System.
Err is a PrintStream. System. Err works like System. Out except it is normally
only used to output error texts. Some programs (like Eclipse) will show the
output to System. Err in red text, to make it more obvious that it is error
text.
7.
Difference between http and https.
HTTP
|
HTTPS
|
URL begins with “http://”
|
URL begins with “https://”
|
It uses port 80 for communication.
|
It uses port 443 for communication
|
Unsecured
|
Secured
|
Operates at Application Layer
|
Operates at Transport Layer
|
No encryption
|
Encryption is present
|
No certificates required
|
Certificates required
|
8.
What is Key Store?
Java Key
Store (JKS) is a repository of security certificates, either authorization
certificates or public key certificates - used for instance in SSL encryption.
9.
Write a Java program to print Fibonacci series.
10.
Difference between Static and Non-Static variable/Method.
Static
|
Non-static
|
Static members are one per class
|
Non-static Variables are 1 per instance.
|
Static members are accessed by their class name which
encapsulates them
|
Non-static members are accessed by object reference.
|
Static methods can be accessed directly from the class
|
Non-static methods (or instance methods as I like to call
them) have to be accessed from an instance.
|
static members can't use non-static methods without
instantiating an objet
|
Non-static members can use static members directly.
|
static constructor is used to initialize static fields
|
Non-static fields normal instance constructor is used.
|
11.
What is immutability in java?
Once created the objects state cannot be changed .E.g. string
12.
How to create read only values in java.
Using final keyword
Final int a=4;
13.
Difference between String and StringBuffer.
String
|
StringBuffer
|
String is used to manipulate character strings that cannot be
changed (read-only and immutable).
|
StringBuffer is used to represent characters that can be
modified.
|
String is slow when performing concatenations because
concatenating a string created new object.
|
StringBuffer is faster when performing concatenations.
|
String is immutable
|
StringBuffer is mutable
|
String is not synchronized
|
StringBuffer is synchronized
|
14.
Difference between Hashmap and Hashtable.
·
Hashtable is synchronized but Hashmap is not.
·
Hashtable can't contain null values but Hashmap permits null
values.
15.
Difference between Iterator and Enumeration.
·
Iterator has remove () method but Enumeration do not have.
·
Iterator is used to Add and remove object, enumeration is used
to traverse and fetch objects.
·
Iterator is used to manipulate text but Enumeration is used for
read-only access.
16.
Define Class-object relationship.
Object
- Objects have states and behaviors. Example: A dog has states-color, name, and
breed as well as behaviors -wagging, barking, and eating. An object is an
instance of a class.
Class -
A class can be defined as a template/ blue print that describe the
behaviors/states that object of its type support.
Class
is a blueprint while objects are actual objects existing in real word.
17.
What to test while
testing Client-server application.
·
Performance
·
Load
·
Integration between multiple components
·
MUT
·
SOAK testing
·
Multiple clients for same server
18.
How to Read/write excel file in Java.
19.
Difference between Method Overloading and Overriding.
|
Method Overloading
|
Method Overriding
|
|
Arguments Must change
|
Arguments Must not
change
|
|
Return type Can change
|
Return type Can’t
change except for covariant returns
|
|
Exceptions Can change
|
Exceptions Can reduce
or eliminate. Must not throw new or broader checked exceptions
|
|
Access Can change
|
Access Must not make
more restrictive (can be less restrictive)
|
|
Invocation Reference
type determines which overloaded version is selected. Happens at compile
time.
|
Invocation Object type
determines which method is selected. Happens at runtime
|
20. Write a java program to count number of unique words separated by comma (,) and their occurrence from text file.
21.
Difference between int & INTEGER.
int is
a primitive type. Variables of type int store the actual binary value for the
integer you want to represent. int.parseInt("1") doesn't make sense
because int is not a class and therefore doesn't have any methods.
Integer
is a class, no different from any other in the Java language. Variables of type
Integer store a reference to Integer objects, just as with any other reference
type. Integer.parseInt("1") is calling the static method parseInt
from class Integer (note that this method actually returns an int and not an
Integer).
int type Declaration:
int count;
·
count is a primitive
·
count stores 32 bits of information (in the range
Integer.MIN_VALUE to Integer.MAX_VALUE)
·
Literal integers (e.g. 123 or 0x7b) are of type int
Integer type Declaration:
Integer count2;
·
count2 is an object reference
·
count2 points to an object of type java.lang.Integer (or to
null)
·
The object count2 points at has an int member variable as
described above.
To be
more specific, Integer is a class with a single field of type int. This class
is used where you need an int to be treated like any other object.
22.
Difference between abstract class and interface.
Abstract Class
|
Interfaces
|
An abstract class can provide complete, default code and/or
just the details that have to be overridden.
|
An interface cannot provide any code at all, just the
signature.
|
In case of abstract class, a class may extend only one
abstract class.
|
A Class may implement several interfaces.
|
An abstract class can have non-abstract methods.
|
All methods of an Interface are abstract.
|
An abstract class can have instance variables.
|
An Interface cannot have instance variables.
|
An abstract class can have any visibility: public, private,
protected.
|
An Interface visibility must be public (or) none.
|
If we add a new method to an abstract class then we have the
option of providing default implementation and therefore all the existing
code might work properly.
|
If we add a new method to an Interface then we have to track
down all the implementations of the interface and define implementation for
the new method.
|
An abstract class can contain constructors.
|
An Interface cannot contain constructors.
|
Abstract classes are fast.
|
Interfaces are slow as it requires extra indirection to find
corresponding method in the actual class.
|
23.
Difference between Serialization and synchronization.
·
Serialization is a process by which object instance is converted
into stream of bytes.
·
Synchronization ensures that object data is into accessed by
multiple threads at the same time.
24.
Difference between sleep and wait. Which is better?
·
Wait is better than sleep.
·
Sleep cannot be waken but Wait can be woken using notify method.
·
Sleeps do not release lock but Wait releases lock.
25.
Difference between Array and ArrayList.
·
Array size is fixed at the time of declaration. We can’t modify
it.
·
ArrayList size is not fixed at the time of declaration. We can
change its contents.
26.
Difference between Set and Map.
·
Set – It is also an interface to represent linear collection
with no duplicates. Order of insertion is not maintained. Example:- Harshest, Tree
Set.
·
Map – It represents an indexed collection i.e. key-value pairs.
Example: - Hashmap.
27.
What is AJAX?
·
AJAX stands for
Asynchronous JavaScript and XML. AJAX is a new technique for creating better,
faster, and more interactive web applications with the help of XML, HTML, CSS
and Java Script.
·
Ajax uses XHTML for
content and CSS for presentation, as well as the Document Object Model and
JavaScript for dynamic content display.
·
Conventional web
application transmit information to and from the sever using synchronous
requests. This means you fill out a form, hit submit, and get directed to a new
page with new information from the server.
·
With AJAX when submit is
pressed, JavaScript will make a request to the server, interpret the results
and update the current screen. In the purest sense, the user would never know
that anything was even transmitted to the server.
·
XML is commonly used as
the format for receiving server data, although any format, including plain
text, can be used.
·
AJAX is a web browser
technology independent of web server software.
·
A user can continue to
use the application while the client program requests information from the
server in the background
·
Intuitive and natural
user interaction.
·
No clicking required only
Mouse movement is a sufficient event trigger.
·
Data-driven as opposed to
page-driven
28.
Write a java program for swapping of two numbers
29.
What is final modifier?
The final modifier keyword makes
that the programmer cannot change the value anymore. The actual meaning depends
on whether it is applied to a class, a variable, or a method.
·
Final Methods- A final method cannot be overridden by
subclasses.
·
Final Variables- A final variable cannot be changed once it is
initialized.
·
Final Classes- A final class cannot have subclasses.
30.
Write a java program for factorial of a given number.
31.
What is the different between inheritance and interface?
·
Inheritance:
In java classes can be
derived from classes. Basically if you need to create a new class and here is
already a class that has some of the code you require, then it is possible to
derive your new class from the already existing code. This concept allows you
to reuse the fields and methods of the existing class without having to rewrite
the code in a new class. In this scenario the existing class is called the
super class and the derived class is called the subclass.
·
Interface:
In Java language an
interface can be defined as a contract between objects on how to communicate
with each other. Interfaces play a vital role when it comes to the concept of
inheritance. An interface defines the methods, a deriving class (subclass)
should use. But the implementation of the methods is totally up to the subclass.
32.
Write a Program to search
in pdf.
33.
What are Access Modifiers in Java?
·
Default: A variable or method declared without any access
control modifier is available to any other class in the same package
·
Public: A class, method, constructor, interface etc. declared
public can be accessed from any other class
·
Protected Variables methods and constructors which are declared
protected in a superclass can be accessed only by the subclasses in other
package or any class within the package of the protected members' class
·
Private: Methods, Variables and Constructors that are declared
private can only be accessed within the declared class itself.
Non-access Modifiers: final, abstract.
34.
What is the difference between abstraction and encapsulation?
Encapsulation:
- it means binding up of data and methods it means the concept of class in
which we put together the data members and methods or function members.
Abstraction:
- it means that hiding the background details which are not useful to the user
for it we use normally private or protected access specifier by it data is not
let free to move around the system.
1) Abstraction
is implemented in Java using interface and abstract class while Encapsulation
is implemented using private, package-private and protected access modifier.
2) Encapsulation is also called data hiding.
3)
Design principles "programming for interface than implementation" is
based on abstraction and "encapsulate whatever changes" is based upon
Encapsulation.
35.
What is i18n and L10n?
·
I18n stands for Internationalization (18 char between I and n).
·
L10n stands for Localization (10 char between l and n.)It is the
means by which i18n applications can be used for local regions.
·
What is the difference between Inheritance and Interface?
36.
Write a program to reverse a String in Java.
37.
What are the difference between Java and JavaScript?
Java
|
JavaScript
|
Java
is an Object Oriented Programming (OOP) language
|
JavaScript
is a scripting language
|
Java
is very much Complex.
|
JavaScript
s comparatively easy.
|
Java
contains rich set of commands.
|
JavaScript
contains a much smaller and simpler set of commands
|
Java
can stand on its own that creates "standalone" applications.
|
JavaScript
must (primarily) be placed inside an HTML document to function
|
Java
must be compiled into what is known as a "machine language" before
it can be run on the Web.
|
JavaScript
is text-based. You write it to an HTML document and it is run through a
browser.
|
38.
What is the base class of all classes?
java.lang.Object
39.
Write a Java program to print Palindrome number after number
n passed by user.
40.
What is the difference between Checked and Unchecked exceptions?
The
compiler forces you to either catch checked exceptions or throw them to the
calling method. For e.g. IOException.
Unchecked
exceptions (Runtime exception) are due to programming bugs (for ex. index out
of bound exception). The compiler expects you to handle this in the code so it
does not force you to catch unchecked exceptions. Exceptions extending Runtime
Exception are unchecked.
41.
What is Auto boxing and unboxing.
Auto
boxing-Automatic conversion of primitives into corresponding objects wrapper
classes.
Unboxing
- Automatic conversion of wrapper classes into primitives.
Need
The
collections like ArrayList store only the objects so primitives need to
converted to object wrapper classes.
Auto
boxing/Unboxing helps to do automatic conversion.
42.
What is the difference between executequery and executeupdate.
·
executeQuery method is used to execute SQL which returns
ResultSet.
·
executeUpdate method is used to execute update queries like
insert, update, or delete.
43.
What is Annotation?
An
annotation indicates that the declared element should be processed in some
special way by a compiler, development tool, and deployment tool or during
runtime.
44.
What is the Difference between put and post?
HTTP PUT:
PUT
puts a file or resource at a specific URI, and exactly at that URI. If there's
already a file or resource at that URI, PUT replaces that file or resource. If
there is no file or resource there, PUT creates one HTTP 1.1 RFC location for
PUT.
HTTP POST:
POST
sends data to a specific URI and expects the resource at that URI to handle the
request. The web server at this point can determine what to do with the data in
the context of the specified resource.
45.
What are Java Annotations?
Java 5 comes with several pre built annotations
·
Override
·
Deprecated
·
SupressWarning
·
Retention
·
Target
46.
Write a program to generate 15 random integers between 0 and 10.
Random
r = new Random();
for(int i=0;i<15;i++){
System.out.println(r.nextInt(10));
}
47.
Write a program to fetch unique elements from Array.
48.
Write a program to transpose a Matrix.
49.
Difference between Throw and Throws.
·
Throws – used to advertise that the method might throw some
exceptions.
·
Throw – used to throw exception from method definition.
50.
Write a difference between System.exit(0) and System.exit(1).
·
System.exit(0) is used in any method to come out of the program.
It terminates the program normally where as
·
System.exit(1) terminates the program because of some error
encountered in the program.
