java interview questions for experienced. Popular questions

 How to remove duplicate elements from a list using java8 and sort  example:- "abc","abc","xyz","pqr","pqr" output:- "abc","pqr","xyz". what are the status of the object in case of java hibernate :- persistent , transient  What are the memory blocks in case of stack What is the optional class  Why do we require only one abstract method in case of functional interface ? How do we use functional interface with lambda expression What is actuator ? what is indexing in database  How do you write junit for the method which does not return any thing How many types of executor service ? what are their implementation  what is cyclic barrier and count down latch ? What is cascading in hibernate with an example  what is transaction management in hibernate  can immutable class be singleton and vice versa ? What is solid principal in java ? what is atomicity? what are the scopes of spring bean? What is inversion of cont...

Check :- basic understandng of loops variables methods object class constructors few keywords ======================================================================= 2nd Day : Java-> Class , object:- basic . with multiple code example Constructor Class and Object - Constructor in Java Theory - Constructor Example - Approach :- function :- basic structure of a program class{ instance variable static variable static block static methods cpnstructors methods()-> local variable objects business logic ) Class and Object - 01:21:23

Introduce yourself  Tell me about your last project  Why were you migrating your application from IBM web sphere to Tomcat What kind of application was it ? (Spring mvc, normal rest api) Complete flow of your application ? What and all services you were consuming in your application? Why were you consuming those services ? How did you do it ?  What and technology you have used ? How did you work on exception handling in your application ? How can you write your own custom exception? What are the response code in case of rest services example 404,200 and in what case do you get these error ? How have you implemented REST API , how have you mapped request url to nay method? What is put , pots and delete method ? Complete end to end flow and functional understanding of the project ? How have you implemented database connection in your project ? How can you connect multiple database in your application? Have you worked on junit? Have  you worked on any ci/cd tool? How yo...

What is multithreading concept? What is a thread? How many ways you can create a thread? Which one is better option to create a thread, by extending a thread class or by implementing Runnable interface? What is sleep method. What is yield method? What is join method? What is wait , notify and notifyAll methods , and why do they belong to Object class? What are the states of a thread ? what is a daemon thread ? What is callable? Difference between runnable and callable ? What is future object ? Programming of Future object ? What is ThreadPool ? What is executor and all its example ? What is countDownlatch and cyclic barrier ? Programming example of CountDownLatch and Cyclic barrier?  Producer consumer example ? How to create your own blocking queue? Concurrent HashMap? What is synchronization ? What is synchronized block and method ? What is volatile ? IllegalThreadStateException ?

What is the difference between abstraction and polymorphism? What is encapsulation? How to print repeated no. stored in an array? using hash Set , using Hashmap How to swap to string without using third variable ? public class SwapToString { public static void main(String[] args) { // TODO Auto-generated method stub  String a="Hellow"; String b="World"; System.out.println("String before swap   "  + a+ "   "+b); a=a+b; b=a.substring(0,a.length()-b.length() ); System.out.println(b); System.out.println(a); System.out.println(a.substring(b.length())); } } ----------------------- o/p String before swap   Hellow   World Hellow HellowWorld World what and all design pattern you have worked on? What is factory design pattern ? What is singleton design pattern ? How do you create your own singleton class ? How do you create your own immutable class? Why is String immutable? What is the difference between String a="abc"; and String a = new ...

What is Microservice , can you describe Microservice Architecture ? Which protocol you have used in microservices? Write a json example. How do multiple microservices interact with each other ? How to define producer and consumer services in discovery server? What is thread ? Write a program to start a thread? What will happen if you restart a thread? Suppose there are 3 thread t1, t2, t3 , t1 thread generates even no , t2  generates odd and t3 generates prime. How will you make sure that first even no gets printed then odd and then prime no? Write a produce consumer program with a concurrent API ? You can use CountDownLatch . Write a program to remove duplicate elements from a list ? Suppose there is a list of student and that student class contains 3 fields which are StudentName , Student ID and a list of StudnetMarsks. Sort the students based on the highest marks obtained by them ? Highest marks is nothing bot the sum of all the marks obtained in all the subjects . Can we write ...

How to implement your own equals() and hashcode() methods in java? How to implement your own ArrayList in java? How to make your own immutable class in java? How do you append a first name to a list of name using stream? For example if you have a list of name and you want to append Dr. before first name how to do that using java 8? What is strategy in java while implementing your own equals() method? What is upcasting and downcasting What is class cast exception? What is lambda expression ? When to use abstraction and interface ? What is functional interface ? What is abstraction and encapsulation? Give an example of encapsulation?

Core Java         Basic understanding of JVM , JDK ,JRE       Basic understanding of Memory        OOPS Concept Encapsulation        Abstraction Polymorphism Inheritance        String l       String Builder & String Buffer       Arrays       Garbage Collection       Exception Handling       Method  & Classes       Constructor    Serialization Collection Design Pattern  Multi-threading  Spring JDBC Hibernate Spring MVC Spring Boot Spring Security Spring Batch JavaScript Microservice REST API JPA Server JAVA 8 Features Junit Latest Java features of Java 9 ,10,11,12,13,14 Oracle SQL PL/SQL Agile methodology Git MAVEN Jenkins(CI/CD tools) Swagger SonarQube Tomcat Programs Basic Concept of Docker Basic Unix Command Basic Concept of AWS ElasticSearch RabbitMQ Spring Cloud C...