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Mastercard Java Interview 2022 — Transcript · YTtoTranscript

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Mastercard Java Interview 2022

CloudTech · 2,146 words · 11 min read · EN

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Below is the complete, readable transcript of Mastercard Java Interview 2022 by CloudTech on YouTube. Read the full text, copy any part you need, or generate a transcript for any video with our free tool.

hi guys welcome to cloud tech in this interview we are going to discuss a real mastercard interview question that we got from students who got placed in mastercard and at the end of this interview we are going to solve one java 8 coding problem so let's start with the interview okay uh can you tell me what is an

optional class in java 8 yes so uh starting from uh when you when you write the code uh there is a lot of problem with null checks so we have to do a lot of null checks optional class is the one who solves this problem using optional class you can reduce the number of null check and

when you perform certain operation at the end of the operation you either get the result or you get null back so optional is used in that case and it is introduced in java 8 okay what is functional interface functional interface is is an interface which has only one abstract method and that interface is generally annotated

with at the right uh functional interface and there are various functional interfaces in java 8 for example or runnable is a functional interface um predicate is a functional interface so in a sense it has one abstract method and there can be multiple default methods in functional interface okay so what is predicate a predicate is also a functional

interface and you can you can write one test condition using predicate so predicate is a test condition for example you have a list and there are various elements in the list and integer elements in the list and you want to filter only elements which are greater than 18 for for example who can vote

so you can perform this thing using predicate you can write a predicate and you can write condition as age is greater than 18 and to the filter method of the stream you can pass this predicate to get the filtered results do you know method reference in java yes so method reference uh generally to

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call a method you have to create an instance of the class just for calling the method so consider there is an interface which is a functional interface and that is one class that implements that functional interface so you implement uh the class just for overriding that method or giving implementation of that method

so java has provided us with the convenience syntax where to call a method from a class you can write uh you can use method reference for example to call a println method from your system.out you can write dot out and then the method reference operator and then actual method name which is println so you can use method

reference to call either static methods or instance methods okay let us consider i have a list of stream and i have to convert that into an array by using java so can you do it yes so uh you have a stream uh so to get the stream i can use list dot stream and

to convert that to array there is one method uh known as to add it so when i call to array on my stream it returns the array representation of your stream so whatever elements will be there in the stream will be given to you back in the in the array itself using two other

methods no okay what are the collections which you have worked on i have worked on various collections uh hashmap or linked list parallelist or concurrent hashmap or site headset so these are collections okay consider i have a list of hundred elements okay and i wanted to insert few elements in that list and this operation

is going to be frequent so which collection you will prefer either a list or linked list okay uh so you have hundred elements and you have to insert in between the list right yeah so in this case uh as the insertion is frequent i'll go for linked list because link list provides a faster insertion of

elements in between the list because it just changes uh the references while inserting the element okay okay what is mean by fail fast and fail separator in java fail fast and fail ship generally while iterating through your collection okay so you are iterating through your list for example and if some other thread

tries to modify the list on which you are iterating in that case there is a concurrent modification exception so this is fail fast fail fast means whenever whenever there is a collection on which you are iterating and some structural changes happen to that collection then your code should fail it results in concrete modification exception so this

is fail fast fail safe is where while you are iterating over a collection you are given a copy of the collection so you you don't iterate on the original collection you iterate on the copy of collection so whenever the underlying structure is changed your iteration is not hampered with that this is failsafe where you are working

on copy so fail fast is arrow is linked list or all fail fast and concurrent hash map copy on write analysts are all fail safe okay do you know what is mean by array index out of bound exception and when it occurs uh array index out of bond exception uh is when you are trying to

reference an element uh which is suppose your array has a capacity of 10 that means it starts from zero and there are uh there is a index of nine so it starts from zero till index of nine and you try to access 11th or 12th index of that array then it it gives you array

index out of bound exception so it's a logical error where you are trying to reference an element which is uh currently not present or and it doesn't have that much capacity till now no okay okay fine so what kind of code repository you are using for your project we are using uh get few of our projects

are in get uh if you are in azure but generally we use git for our uh project what is the use of gate pull and gate post command uh git pool is where uh in the origin uh so if if you are working on your local machine and your branch is checked in uh in the

git repository so if you want the latest code from the repository then you do get pull the git pull gives you or pulls the latest code from the git repository push is where you make some changes on your local machine and you want to add those changes to the git repository remote repository in that case you use a bit

push let us consider there is a scenario there are two developers working on their respective branch dev one and dev two okay now they have raised the merge request to merge their code changes into master branch okay first developer is able to successfully merge his code okay but second developer is getting some

conflicts so why this is happening okay so uh there is a developed branch okay which is a common branch and now two developers are working on two features so they create two branches feature one branch and feature two branch okay now feature one branch is merged into my develop branch so till now everything is

fine but while the developer who is trying to merge feature two into the develop branch we will get conflict because uh the developed has moved one step further of its current state so in this case uh the feature two developer has to pull the develop branch and then emerges changes after resolving conflicts then only he can merge his

pull request to the double branch okay fine so have you came across a situation like your project is running on your local system but it is not running on qa or production environment uh yes i have worked uh on various projects and found this scenario frequently the code works on local machine but it

never it sometimes does not work on the production machine or the virtual machines and the reason yeah how do you resolve it uh reason being uh on my local machine suppose uh there is there is a code to create a file into a directory but when i run this code on my virtual

machine there i might not have permissions or for example i am trying to access some file location or for example the memory that i have on my local machine and the memory that i get on my virtual machine to solve this problem uh we have something called as uh docker where the phone running on your local

machine uh will always run on your virtual machine using docker so docker is the solution for this okay do you know what is ci cd yes ci cd is ci is continuous integration and cd is continuous delivery or sometimes it is called as continuous deployment so cici is continuous integration where whatever code you do should be

continuously merged into your branches and cd is where whenever you merge your code to that branch your bill should be triggered and it should be deployed to your environment so ci is where continuous integration uh you should merge your code with the branches and bill should be triggered and cd is where your new artifacts after building should

be deployed to your actual environment and that should be tested okay and which tool you are using for building your projects in my current project i am using jenkins but in my previous project i used azure tfs okay and how do you build your project by using maven is there any other repo

so we use uh build tool as meven uh in my in my previous project we used to use ib y but uh as meven is um used nowadays so we are also sticking with maven maven build is the command uh no we haven't we can do and the dependencies which you are downloading using maven are those

dependencies coming from your own company repository or it is a general maven repository so in previously we were using central repository but uh due to compliance issues um we are now using our own uh company's repository so we have our own repository and there is a team movement this is a repository which has all the

artifacts so we are not using central repository we are using uh the managed repository by the company okay fine i have provided a code snippet in chat box can you copy it in your editor and share your screen yeah so i am copying it and i am uh yeah so i have shared my eclipse

uh yeah i can see so uh let us consider i have to generate random numbers okay so can you write the code to generate it by using java 8 yes so i'll make use of a random class okay random r and dom random visible i'll instantiate a random okay then i'll use uh

i'll try to use random dot i'll try to get ins out of it i'm i'm going to print in and i'm going to use forage so i'm going to use uh system dot out and this is the method reference okay okay double colon and then i'm going to use um println to print all

all the ends okay so this is one and you have yeah you have to print ten numbers ten numbers okay so i'll i'll stop this and uh to print ten numbers i'm going to use a limit i am going to write 10 so this will limit my numbers to 10 so this will print 10

random numbers okay so these numbers are very large numbers can you try to print the numbers within a range like 100 yeah so while getting the hinge i can uh pass the initial starting point and the ending point so 1 200 is what we want i'm going to run this program and these these are the numbers from 1 200.

okay so can you try to sort this is it possible for you to sort these numbers yeah so i'll try to use uh sorted so this will sort the elements in ascending order but this is the ascending order okay fine okay i'm done from my side do you have any question uh i don't have

any questions thank you yeah thank you bye thanks