This repository will contain all the java, spring, hibernate, mysql, elastic search, thread, related questions.

• OOPS

  • Solid principle of java
  • Object Cloning in Java
  • Types of set in java
  • What is OPPS concepts?

• Thread

  • Blocking queue
  • Producer and consumer approach
  • final syncronization variable or method can be possible?
  • Why is synchronized block better than synchronized method?
  • Why Wait(), Notify() and NotifyAll() Defined in Object Class?

• Java-8

  • Wha is metaspace in java 8?
  • Supplier Interface in java
  • Predicate Interface in java
  • Parallel Stream with findFirst?
  • Stateless and stateful operations of stream
  • How parallel stream works?
  • What is major diff. between forEach and stream?
• Why Streaming?(FileUpload)
• Types of GC
• Explain internal working of GC(Garbage Collector)?
• Allocating max head size for jar?
• Types of classloader and Bootstrap classloader?
• use of transient keyword
• HashMap is on which data structure?
• How ConcurrentHashMap Works Internally in Java?
• Eliminated permGen memory block from java 8, why?
• Optional with stream() can be applied or not?
• How to make class immutable?
• How many different ways to create objects in Java?
• Why string is immutable class?
• Is java a pure object oriented programming language?

• @Bean can be used at class level?
  • https://docs.spring.io/spring-javaconfig/docs/1.0.0.M4/reference/html/ch02s02.html
  • https://www.baeldung.com/spring-bean-annotations
• What is difference between spring and spring boot?
• Types of autowiring in spring
• How to include one package to another package?
• Use of @ComponentScan annotation?
• Can we use @component instead of @service in spring?
• Why spingboot?
• How spring transaction management work?
• What is a transitive Maven dependency?
• Maven Dependency Scopes
• Types of IOC containers in Spring Framework
• What is servlet controller?
• What is sping boot acuator
• What is dev tools in spring? For what purpose it is used?
• What is spring MVC?
• Write spring annotation with cron expression for a job which execute at every 5 min. Is at main class we to annotate any annotaion?If yes then with which?
• When to use Qualifier and Primary in Spring?

http://hibernate.org/orm/documentation/5.4/

• What Is a Second-Level Cache?
• Different annotations in hibernate?
• @OneToMany mapping?
• What is the use of @inheritance?
• How to use super class and subclass as individual entity?
• Where we can use @manyToMany mapping, explain we example?
• What is disadvantage of hibernate?
• What is the "N+1 selects problem" in ORM (Object-Relational Mapping)?

• Self join of same table for username and manager name.
• What is the use of Composite key? - MySql Tuning?
• How to delete only duplicate/copy from employ table?
• How to fetch first and last record from the table?
• Write MySql query to print second highest salary from employee table?

• Best practice for writing naming convention of api URI.
• Difference between PATCH, PUT and POST Method?
• REST API using POST instead of GET

https://www.elastic.co/guide/en/elasticsearch/reference/current/docs.html

• different types of queries
• less than and greater than
• How to fetch total record no. of a query?
• What is token filter(stopwords, tokenizer, etc)?
• What is analyser? How we can use this in ES?
• How to create mapping?
• What are different Http methods use in ES query?
• [Instead of POST when we PUT some record/doc then what will happen?]

• Why double checking in Singleton?
• Singleton real world example.
• What is proxy class?
• How to create proxy design pattern?
• What is abstract design pattern?
• What is Command design pattern? Where we can use this?
• What are the different design pattern use in Spring framework?
• How to prevent Singleton Pattern from Reflection, Serialization and Cloning?
• What is microservice design pattern?

• What is a transitive Maven dependency?
• Dependency scope of maven
• What is main purpose of maven?
• How maven search dependency in your system? Explain.

• What is EC2 instance?
• For what purpose S3 bucket is used?
• Public and private S3 bucket?

• How to prevent a network or service failure from cascading to other services?
• How to manage Latency and Fault Tolerance for Distributed Systems?

• 100 doors
• 9 balls 1 different weight
• Find the fastest 3 horses

• Different HTTP types? What is PATCH http method?
• What will be differrent reason when below 2 mb file uploaded and above doesn't through a api?

• Find 2nd lagest number in an array? Input: {23,10,34,23,20} -> output: 23

    set arr = [23,10,34,23,20]
    int lengthOfArray = arr.length();
    int max = 0;
    int secondMax = 0;
    for(int i=0;i<lengthOfArray;i++){
    if(arr[i]>max){
    secondMax = max;
    max= arr[i];
    }
  
    s.o.p(secondMax);
  
    }
  

• Occurance count string = "AAABBCCCDDAACCEE" then ouput : 3A2B3C2D2A2C2E

        public class Main
      {
          public static void main(String[] args) {
  
              String str = "AAABBCCCDDAACCEE";
              int strLength = str.length();
              char ch = str.charAt(0);
              int counter = 0;
              for(int i=0;i<strLength;i++){
                  if(ch == str.charAt(i)){
                      counter=counter+1;
                      continue;
                  } else {
                      System.out.print(counter);
                      System.out.print(ch);
                      counter = 1;
                      ch = str.charAt(i);
                  }
              }
              System.out.print(counter);
              System.out.print(ch);
          }
      }
  

• all permutation of a string = "ABC" then ouput : ABC, ACB, BAC, BCA, CAB, CBA