telephonic interview on java, microservives

Core Java

1.)    Can you tell me briefly about oops principle with a real time example?

Inheritance:- It is a way in which child object inherits common properties and behavior

From parent object.

Use of this is to promote code reuseability.

Polymorphism:-

2 types of polymorphism are there compile time(overloading ) and runtime (overriding).

Overloading:- to change the behavior of method based on change in arguments.

Overriding:- To change the behavior of method defined in parent class in child class.

Encapsulation:- It is used to bind data and behavior in together.It is promoted by making

Instance varaibles private and access via getter and setter.

Abstraction:- To hide implementation details from the client and exposing via interface or abstract class is know as abstraction.

Example :- HashMap

Map map = new HashMap();

m.put(“key”,”value”);

As we can see, we can create and use the operations but underlying implementation is hidden so implementation is abstracted from client.

Internally, HashMap uses Entry array, then declare private and public access methods that the encapsulation.

A realization of your desired abstraction.

Encapsulation = Abstraction + Data Hiding

2.)    What is the use of POJO(getter and setter) in java?

It is encapsulation principle.

The fields of a class can be made read-only or write-only.

A class can have total control over what is stored in its fields.

The users of a class do not know how the class stores its data. A class can change the data type of a field and users of the class do not need to change any of their code.

3.)    Difference between ArrayList and LinkedList?

                  Storage

ArrayList:- dynamic array

LinkedList:- doubly LinkedList

   Use case

ArrayList:- ArrayList is better for storing and accessing data.

LinkedList:- LinkedList is better for manipulating data.

4.)    Below Code snippet and tell the output.

Void a() throws exception()

{

B();

Return “a”;

}

Void b(){

Try{

Return “b”;

}catch (Exception e) {

Return “e”;

}finally {

Return “f”;

}

}

a.)    Incase no exception is thrown

b.)    Incase exception is thrown

Always return a and in case exception is re- thrown then nothing will be printed .

         Spring

5.)    What is spring boot, spring eureka ,  spring config?

Spring boot:- simplify the bootstrapping and development of a new Spring application.

Spring eureka:- used to register services to repository.

Spring config:- to find out the end point of eureka server and other configurations

6.)    How to achieve Loading balancing and fault tolerance ?

Using Ribbon and Hystrix.

7.)    Difference between .properties and .yml file and which one is good.

Difference between properties and yml is duplication of prefixes for same category.

YML Is more human readable.

Can configure different profiles in single file using yml.

8.)    Can we configure different properties file like yml for different profiles?

Yes.

9.)    Difference between POST and PUT http methods?

PUT is idempotent, so if you PUT an object twice, it has no effect. This is a nice property, so I

would use PUT when possible.

POST is non-idempotent, when you need the server to be in control of URL generation of your resources. Use PUT otherwise. Prefer PUT over POST.

Example:- POSTing twice with the same data means create two identical users with different ids. PUTing twice with the same data creates the user the first and updates him to the same state the second time (no changes). Since you end up with the same state after a PUT no matter how many times you perform it, it is said to be "equally potent" every time - idempotent. This is useful for automatically retrying requests. No more 'are you sure you want to resend' when you push the back button on the browser.