Interview Questions

1.Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior.

2.Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

3.Members of a Java interface are public by default. A Java abstract class can have the usual flavors of class members like private, protected, etc..

4.Java interface should be implemented using keyword “implements”; A Java abstract class should be extended using keyword “extends”.

5.An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces.

6.A Java class can implement multiple interfaces but it can extend only one abstract class.

7.Interface is absolutely abstract and cannot be instantiated; A Java abstract class also cannot be instantiated, but can be invoked if a main() exists.

8.In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.

Use case diagram, activity diagram, Collaboration diagram. 

Use case diagram :

It describes the business environment. Its primary goal is to show the series of events and actions within any given process that will be performed by an actor.  

Activity diagram:

The activity diagram is important because it gives an outline of the work flow within the business as well as the activities and action completed. 

For instance with a company, there is likely to be more than one department. In such a case each department, will have different access levels to the system. 

So if there’s a Medical, HR and Accounts team they will only have access to screens that relate to each. 

The activity diagram will highlight the differences within the departments which will be very helpful for developers when they are designing and coding. 

Collaboration diagram:

A collaboration diagram, also called a communication diagram or interaction diagram, is an illustration of the relationships and interactions among software objects in the Unified Modeling Language (UML). The concept is more than a decade old although it has been refined as modeling paradigms have evolved. 

A JAR file (short for Java Archive) is a ZIP file used to distribute a set of Java classes. It is used to store compiled Java classes and associated metadata that can constitute a program

array_flip exchange the keys with their associated values in array ie. Keys becomes values and values becomes keys.

<?php
$arrayName    = array("course1"=>"php","course2"=>"html");
$new_array    = array_flip($arrayName);
print_r($new_array);
?>

OUTPUT :

Array
(
[php]     => course1
[html]    => course2
)

the layer that establishes ,manages and terminates the session between two communticating devices

This question focuses to check your ability to handle situations. Do not answer this question with anything that states retaliation. Talk about handling the situation with patience and relaxed mind set. You can answer it as “ If the customer on the other side of the phone line is angry i will first try calming him and ask him his/her problem. After that I will try sufficing the best solution keeping in mind his problem. In this sector customer satisfaction is very important and thus it will be my primary goal.

A destructor is automatically called when the object is destroyed. A virtual destructor in C++ is used primarily to prevent resource leaks by performing a clean-up of the object.

Example:

“I have no problems with change. I am sure in my ability to regulate my actions of behaviors as needed, and take up myself adaptable to all situations – not just change.”