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03: Java GC tuning for low latency applications

This assumes that you have read the basics on Java GC at Java Garbage Collection interview Q&A to ascertain your depth of Java knowledge. This is a must know topic for those who like to work on low latency applications. Q1. In what ways does GC impact latency and throughput...

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03: JMockit interview Q&As & examples on initialising @Injectable fields

This extends 02: JMockit interview Q&As & examples on Expectations & Verifications. We have already discussed that a non-final instance field annotated as @Tested in the test class will be considered for automatic instantiation and injection, just before the execution of a test method. … Read more ›...

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03: JUnit & Mockito Interview Questions & Answers

JUnit & Mockito interview questions & answers extends 5 Java unit testing interview Questions and Answers. Unit testing is widely accepted as a “best practice” for your Java code quality. You can also refer to 6 JUnit & JMockit interview questions & … Read more ›...

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03: Kubernetes (aka k8s) interview Q&As – objects & manifest files

Q01. What is a Kubernetes object? A01. One of the key concepts in Kubernetes is the “desired state,” which refers to the configurations of the applications that you want to deploy and run. A desired state includes things like how many instances of applications should be running, … Read more...

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03: Kubernetes (i.e. Minikube) – deploy a spring boot microservice app

This extends Kubernetes (i.e. Minikube) – deploy a node js service.

Docker containers & Kubernetes for deploying Spring Boot microservices. As mentioned earlier in Kubernetes, Docker & Microservices interview Questions & Answers.

Docker gives you application isolation, and solves the dependency hell issues.

…

03: Microservices Architecture design patterns & considerations interview Q&As – Part 2

Microservices Architecture Patterns & considerations

This extends 02: Microservices Architecture design patterns & considerations interview Q&As – Part 1. 3. Decomposition Design Patterns When decomposing the Microservices, we should avoid having tight coupling between the services. This can be achieved by duplicating the data in the required/dependent services. … Read more ›...

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03: Mockito interview Q&As & examples on @Mock, Mockito.mock(…) and @MockBean

Unlike a @Spy where you are spying on a real object, when you mock, you are creating a complete mock or fake object. Q: What are the different ways to mock an object? A: There are 3 ways to mock a dependent class that is sed by the class under...

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03: Mockito to fully mock the DAO layer

This extends Part 1: Unit testing with JUnit, Mockito & Spring by mocking the DAO layer with the Mockito framework. Step 1: Service and DAO layer interfaces and implementations Service Layer

package com.mytutorial;

public interface SimpleService {
    abstract String processUser(int id);
}

package com.mytutorial;

public interface SimpleService {

abstract String processUser(int id);

}

package com.mytutorial;

import javax.inject.Inject;
import javax.inject.Named;

@Named
public class SimpleServiceImpl implements SimpleService {

    @Inject
    SimpleDao dao;

    public String processUser(int id) {
        String name = dao.getNameById(id);
        return "Hello " + name;
    }
}

package com.mytutorial;

import javax.inject.Inject;

import javax.inject.Named;

@Named

public class SimpleServiceImpl implements SimpleService {

@Inject

SimpleDao dao;

public String processUser(int id) {

String name = dao.getNameById(id);

return "Hello " + name;

}

DAO Layer This layer will be mocked by Mockito in the next step. … Read more ›...

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03: Networking basics interview Q&As on VPN, Proxy Server & Reverse Proxy

This post extends the 01: Networking basics interview Q&As on ip address, subnet mask, DNS & gateway with some of the key networking concepts that we face as software engineers & architects. VPN Q1. What is a VPN? A1. … Read more ›...

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03: Q16 – Q17 Java Polymorphism vs Overriding vs Overloading

Polymorphism is the ability of a class instance to behave as if it were an instance of another class in its inheritance tree, most often one of its ancestor classes. Overriding is the means by which you achieve polymorphism. Java Polymorphism vs Overriding vs Overloading explained in detail to handle drill down Java OOP interview questions with ease when quizzed further.

…

03: Scenarios based Java OO concepts & GoF design patterns – Strategy Pattern

The following post improves on the design flaws listed in the previous post entitled 02: Scenarios based Java OO design & GoF design patterns – naive Template Method pattern. Scenario: A company named XYZ Retail is in the business of selling Books, … Read more ›...

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03: Shell script interview Q&As for Java developers

Q1 How will you go about reading a CSV file as shown below?

Portfolio,Account,PositionIndicator,Amount
AA123,CURR-AUD,CREDIT,2244.14000000
AA123,CURR-AUD,CREDIT,5.60000000
AA123,CURR-AUD,DEBIT,2249.74000000
AA123,CURR-GBP,CREDIT,0.01000000
AA123,CURR-GBP,DEBIT,0.01000000

Portfolio,Account,PositionIndicator,Amount

AA123,CURR-AUD,CREDIT,2244.14000000

AA123,CURR-AUD,CREDIT,5.60000000

AA123,CURR-AUD,DEBIT,2249.74000000

AA123,CURR-GBP,CREDIT,0.01000000

AA123,CURR-GBP,DEBIT,0.01000000

#!/bin/bash
 
# $# means number of arguments supplied to the command. In this case the file to to be read
if [ $# != 1 ]; then
    echo "Usage: $0 input-file"
    exit 1
else
    infile=$1
fi
 
# assign file descriptor 3 to input file
exec 3< $infile
 
# read till the end of the file
until [ $done ]
do
    read <&3 myline
 #$? is the exit code, and 0 means success and != 0 means not success. That is no line is read.
    if [ $? != 0 ]; then
        done=1
        continue
    fi
 
    # process file data line-by-line in here
 
    echo $myline
done

#!/bin/bash

# $# means number of arguments supplied to the command. In this case the file to to be read

if [ $# != 1 ]; then

echo "Usage: $0 input-file"

exit 1

else

infile=$1

# assign file descriptor 3 to input file

exec 3< $infile

# read till the end of the file

until [ $done ]

read <&3 myline

#$? is the exit code, and 0 means success and != 0 means not success. That is no line is read.

if [ $? != 0 ]; then

done=1

continue

# process file data line-by-line in here

echo $myline

done

Q2 How will you read and then write to another file?

Portfolio,Account,PositionIndicator,Amount
AA123,CURR-AUD,CREDIT,2244.14000000
AA123,CURR-AUD,CREDIT,5.60000000
AA123,CURR-AUD,DEBIT,2249.74000000
AA123,CURR-GBP,CREDIT,0.01000000
AA123,CURR-GBP,DEBIT,0.01000000

Portfolio,Account,PositionIndicator,Amount

AA123,CURR-AUD,CREDIT,2244.14000000

AA123,CURR-AUD,CREDIT,5.60000000

AA123,CURR-AUD,DEBIT,2249.74000000

AA123,CURR-GBP,CREDIT,0.01000000

AA123,CURR-GBP,DEBIT,0.01000000

#!/bin/bash
 
# $# means number of arguments supplied to the command
if [ $# != 2 ]; then
    # $0 is the script name  $1 is input file and $2 is output file  
    echo "Usage: $0 input-file output-file"
    exit 1
else
    infile=$1
fi
 
# assign file descriptor 3 to input file
exec 3< $infile
 
# read till the end of the file
until [ $done ]
do
    read <&3 myline
 #$? is the exit code, and 0 means success and != 0 means not success. That is no line is read.
    if [ $? != 0 ]; then
        done=1
        continue
    fi
    
   # process file data line-by-line
    
    # append to output file. If you run it more than once, it keeps appending.
    echo $myline >> $2 
done

#!/bin/bash

# $# means number of arguments supplied to the command

if [ $# != 2 ]; then

# $0 is the script name $1 is input file and $2 is output file

echo "Usage: $0 input-file output-file"

exit 1

else

infile=$1

# assign file descriptor 3 to input file

exec 3< $infile

# read till the end of the file

until [ $done ]

read <&3 myline

#$? is the exit code, and 0 means success and != 0 means not success. That is no line is read.

if [ $? != 0 ]; then

done=1

continue

# process file data line-by-line

# append to output file. If you run it more than once, it keeps appending.

echo $myline >> $2

done

Q3 How will you read the file and then write to another file with CSV data in different order? …...

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03: Spring Boot annotations interview Q&As

Q1. What are the core annotations used in a Spring Boot applications? A1. Annotations are used to configure & customize a Spring boot application. @SpringBootApplication This is a core class level annotation that marks the main class of a Spring Boot application, … Read more ›...

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Categories

Blog Archives

03: Java GC tuning for low latency applications

03: JMockit interview Q&As & examples on initialising @Injectable fields

03: JUnit & Mockito Interview Questions & Answers

03: Kubernetes (aka k8s) interview Q&As – objects & manifest files

03: Kubernetes (i.e. Minikube) – deploy a spring boot microservice app

03: Microservices Architecture design patterns & considerations interview Q&As – Part 2

03: Mockito interview Q&As & examples on @Mock, Mockito.mock(…) and @MockBean

03: Mockito to fully mock the DAO layer

03: Networking basics interview Q&As on VPN, Proxy Server & Reverse Proxy

03: Q16 – Q17 Java Polymorphism vs Overriding vs Overloading

03: Scenarios based Java OO concepts & GoF design patterns – Strategy Pattern

03: Shell script interview Q&As for Java developers

03: Spring Boot annotations interview Q&As

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