Quick Prep Java Interview Archives | Page 14 of 28 | 800+ Java & Big Data Interview Q&As

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09: JMockit interview Q&As & examples on matching of argument values

JMockit offers a set of utility fields for making argument matching more generic. 1) anyX fields like anyInt, anyBoolean, anyString, etc. There is one for each primitive type, and the corresponding wrapper class, … Read more ›...

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09: Part 2: Java Tree structure interview questions and coding questions

In the previous post entitled Java Tree structure interview questions and coding questions — Part 1, we looked at a very simple Tree structure. In this example, let’s look at a more complex tree structure with generics. Q. Write classes for a Tripple tree structue as shown below? … Read...

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09: What is wrong with this code? HashMap & Race condition

Q. What is wrong with the following code snippet?


import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class WhatIsWrong implements Runnable {
	
	//shared by threads
	final static Map<String, String> map = new HashMap<String, String>();
	
	
	public static void main(String[] args) throws InterruptedException {
		  ExecutorService pool = Executors.newFixedThreadPool(100);
		    for (int i = 0; i < 100; i++) {
		    	WhatIsWrong wiw = new WhatIsWrong();
		        pool.submit(wiw);
		    }
		    
		    pool.shutdown();
		    pool.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
		
	}


	@Override
	public void run() {
		for (int i = 0; i < 1000000; i++) {
            map.put(Thread.currentThread().getName(), "wow-" + i);
            Object retrieved = map.get(Thread.currentThread().getName());
            if(retrieved == null) {
            	System.out.println("Race conmdition detected!!! Map is in inconsistent state");
            }
        }
		
	}
}

import java.util.HashMap;

import java.util.Map;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

public class WhatIsWrong implements Runnable {

//shared by threads

final static Map<String, String> map = new HashMap<String, String>();

public static void main(String[] args) throws InterruptedException {

ExecutorService pool = Executors.newFixedThreadPool(100);

for (int i = 0; i < 100; i++) {

WhatIsWrong wiw = new WhatIsWrong();

pool.submit(wiw);

}

pool.shutdown();

pool.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);

}

@Override

public void run() {

for (int i = 0; i < 1000000; i++) {

map.put(Thread.currentThread().getName(), "wow-" + i);

Object retrieved = map.get(Thread.currentThread().getName());

if(retrieved == null) {

System.out.println("Race conmdition detected!!! Map is in inconsistent state");

}

A. It is NOT thread-safe as a “HashMap” is not thread-safe as per the Java API, and race conditions can leave the “map” in “inconsistent state“. … Read more ›...

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09: When to use which Java data structure? and why?

List, Set, Map, and Queue(access the ends FIFO or LIFO) are the basic Java data structure interfaces for which there are different implementations to cater for different usage patterns. Java data structure interview questions are very popular, … Read more ›...

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1. Asynchronous processing in Java real life examples – part-1

The scenario based questions are very popular with the job interviewers, and some scenario based questions are related to decoupling and asynchronous (aka non-blocking) processing in Java with message queues/topics, database tables where one process inserts data and another process consumes the inserted data, and Future objects in Java multi-threading....

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1. Set up environment for home coding assignments

Step 1: Setup Java, Maven, and SonarQube

1. Java: Latest possible version. Setting up Java, Maven, and eclipse.

2. Maven 3: For building. Setting up Java, Maven, and eclipse.

3. SonarQube: For code quality.

…

10 Distributed storage & computing systems interview Q&As – Big Data

A distributed system consists of multiple software components that are on multiple computers (aka nodes), but run as a single system. These components can be stateful, stateless, or serverless, and these components can be created in different languages running on hybrid environments, using open-source technologies, open standards, and interoperability.

Q01.

…

10 ERD (Entity-Relationship Diagrams) Interview Q&As

Q01. Can you describe a business domain of a Telecom company offering multiple services to its customers? A01. A Telecom company will have entities such as Customer, Account, Subscriptions & Products representing a business domain. 1) Each customer entity has a name, … Read more ›...

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10 Java web services written test questions and answers

Java Web Services interview Questions & Answers Links: 6 Java RESTful Web services Interview | 11 SOAP Web service interview | 5 JAXB interview Questions & Answers | Java Web Services interview Questions & Answers Q1. … Read more ›...

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10: Find all permutations of a given string – Iteration in Java

Q. Complete the method “Set getAllCombinations(String input) ” where input is any string and the method should return all possible combinations of a given string.


import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

public class WordPermutations {

    public static Set<String> getAllCombinations(String input) {
        throw new RuntimeException("Complete the given code");
    }

    public static void main(String[] args) {
        Collection<String> words = getAllCombinations("abc");
        for (String word : words)
            System.out.println(word);
    }
}

import java.util.Collection;

import java.util.Collections;

import java.util.HashSet;

import java.util.Set;

public class WordPermutations {

public static Set<String> getAllCombinations(String input) {

throw new RuntimeException("Complete the given code");

}

public static void main(String[] args) {

Collection<String> words = getAllCombinations("abc");

for (String word : words)

System.out.println(word);

}

For example: “abc” will have a permutation of 3! … Read more ›...

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10: JMockit interview Q&As & examples on matching anyX field and withX() methods

JMockit offers a set of utility fields & methods for making argument matching more generic. This extends 09: JMockit interview Q&As & examples on matching of argument values 1) anyX fields like anyInt, anyBoolean, … Read more ›...

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10: Part-3: Java Tree structure interview and coding questions

This is an extension to Java Tree structure interview and coding questions — Part 2, and adds functional programming and recursion. Step 1: The Tree interface with get( ) method that returns either a Triple tree or Leaf data. … Read more ›...

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10: Spring, JavaConfig (i.e @Configuration), JPA & Hibernate by example

Example #1 Wiring JDBC Datasource


@Configuration
@ImportResource("application.yml")
public class AppConfig
{
    @Autowired
    private Environment environment;

    @Bean
    public DriverManagerDataSource datasource() {
        DriverManagerDataSource ds = new DriverManagerDataSource();
        ds.setDriverClassName(environment.getRequiredProperty("spring.datasource.driver-class-name"));
        ds.setUrl(environment.getRequiredProperty("spring.datasource.url"));
        ds.setUsername(environment.getRequiredProperty("spring.datasource.username"));
        ds.setPassword(environment.getRequiredProperty("spring.datasource.password"));
        return ds;
    }
}

@Configuration

@ImportResource("application.yml")

public class AppConfig

{

@Autowired

private Environment environment;

@Bean

public DriverManagerDataSource datasource() {

DriverManagerDataSource ds = new DriverManagerDataSource();

ds.setDriverClassName(environment.getRequiredProperty("spring.datasource.driver-class-name"));

ds.setUrl(environment.getRequiredProperty("spring.datasource.url"));

ds.setUsername(environment.getRequiredProperty("spring.datasource.username"));

ds.setPassword(environment.getRequiredProperty("spring.datasource.password"));

return ds;

}

application.yml where the datasource properties are read from.


############
# Datasource properties
############
spring:

  datasource:
    driver-class-name: com.sybase.jdbc4.jdbc.SybDataSource
    url: jdbc:sybase:Tds:mydbhost:5700/my_db
    username: user
    password: pwd

############

# Datasource properties

############

spring:

datasource:

driver-class-name: com.sybase.jdbc4.jdbc.SybDataSource

url: jdbc:sybase:Tds:mydbhost:5700/my_db

username: user

password: pwd

Example #2 Wiring JDBC Datasource with JNDI


@Configuration
@ImportResource("application.yml")
public class AppConfig
{
    @Autowired
    private Environment environment;

    @Bean
    public DataSource dataSource() {
        final JndiDataSourceLookup jndiLookup = new JndiDataSourceLookup();
        final String dataSourceJndi = environment.getRequiredProperty("spring.datasource.jndi");
        return jndiLookup.getDataSource(dataSourceJndi);
    }
}

@Configuration

@ImportResource("application.yml")

public class AppConfig

{

@Autowired

private Environment environment;

@Bean

public DataSource dataSource() {

final JndiDataSourceLookup jndiLookup = new JndiDataSourceLookup();

final String dataSourceJndi = environment.getRequiredProperty("spring.datasource.jndi");

return jndiLookup.getDataSource(dataSourceJndi);

}

Example #3 Wiring the JPA persistence unit processors Callback interface for post-processing a JPA PersistenceUnitInfo. … Read more ›...

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Blog Archives

09: JMockit interview Q&As & examples on matching of argument values

09: Part 2: Java Tree structure interview questions and coding questions

09: What is wrong with this code? HashMap & Race condition

09: When to use which Java data structure? and why?

1. Asynchronous processing in Java real life examples – part-1

1. Set up environment for home coding assignments

10 Distributed storage & computing systems interview Q&As – Big Data

10 ERD (Entity-Relationship Diagrams) Interview Q&As

10 Java web services written test questions and answers

10: Find all permutations of a given string – Iteration in Java

10: JMockit interview Q&As & examples on matching anyX field and withX() methods

10: Part-3: Java Tree structure interview and coding questions

10: Spring, JavaConfig (i.e @Configuration), JPA & Hibernate by example

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