Interview Questions and Answers for 'Orm' | Search Interview Question

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Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.

Q11. What is Volatile keyword used for ?

Core Java

Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached.

Sample Code for volatile

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Q12. Difference between AWS Cloud Formation and AWS AMI ?

Amazon Web Services (AWS)

Ans. AMI is an Amazon Machine Image. It contains the configuration to enable to boot up an EC2 instance with said configuration whereas Cloud formation is a templating language that allows to describe how to build a VPC and also allows you to create AWS services

AMI is templating specific to instances whereas the scope of CloudFormation templating is much bigger. CloudFormation could use AMI for launching instances along with other services.

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Q13. What things you would care about to improve the performance of Application if its identified that its DB communication that needs to be improved ?

Solution

Ans. 1. Query Optimization ( Query Rewriting , Prepared Statements )

2. Restructuring Indexes.

3. DB Caching Tuning ( if using ORM )

4. Identifying the problems ( if any ) with the ORM Strategy ( If using ORM )

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Q14. Which of the following Java feature promotes access protection or Hiding ?

a. Inheritance
b. Encapsulation
c. Abstraction
d. Composition

Core Java

Ans. Encapsulation

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Q15. Why Java is not considered pure OOP's language ?

Core Java

Ans. There are 2 reasons for it.

1. Usage of Primitive types - Though Java provides classes for the primitive data types but as the usage of primitives is permissible, its considered unpure OOP's language.

2. Usage of Static members - Static members belong to the class and not objects and hence not considered fit for pure OOP's programming.

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Q16. Difference between Vector and ArrayList ?

Core Java

Ans. Vectors are synchronized whereas Array lists are not.

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Very frequently asked in phone and walk in interviews.

Q17. What are Marker Interfaces ? Name few Java marker interfaces ?

Core Java

Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote

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Q18. How to configure second level cache in Hibernate ?

Hibernate

Ans. 1. Configure Provider class in Hibernate configuration file.

2. Add Cache usage tag ( read-only or read-write ) in mapping files ( hbm ).

3. Create an XML file called ehcache.xml and place in classpath which contains time settings and update settings, behavior of cache , lifetime and idletime of Pojos, how many objects are allowed.

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This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc.

Q19. What are the ways in which execution time of the code can be improved ?

Solution

Ans. This depends on entirely upon the code type. For example

1.If its just logic, we can try it to short circuit or put the if / switch case with maximum probability in the beginning.

2. Can use faster data structures, for eg - random retrieval instead of sequence / iterator

3. Working with primitive types or even bytes instead of Objects, even though it may result in marginal improvement.

4. If its service call, then service call with bulk load can help

5. If DB Operation, then with use of Indices , Views or using ORM , cache etc.

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Q20. What is cloud computing ?

Cloud Computing

Ans. Cloud Computing is a way of using IT infrastructure with following traits -

1. On Demand Infrastructure
2. Broad Network Access
3. Resource Pooling
4. Rapid Elasticity
5. Measured Service

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Q21. What is the cost of using Cloud Formation ?

Amazon Web Services (AWS)

Ans. Cloud Formation does not have any additional cost but you are charged for the underlying resources it builds.

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Q22. Why is cloud infrastructure so powerful ?

Cloud Computing

Ans. Because it gives the ability to provision infrastructure on Demand with No contracts and strings attached.

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Q23. What is PermGen or Permanent Generation ?

Core Java

Ans. The memory pool containing all the reflective data of the java virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas. The Permanent generation contains metadata required by the JVM to describe the classes and methods used in the application. The permanent generation is populated by the JVM at runtime based on classes in use by the application. In addition, Java SE library classes and methods may be stored here.

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Q24. Write a method to check if input String is Palindrome?

Core Java

Ans. private static boolean isPalindrome(String str) {

if (str == null)
return false;

StringBuilder strBuilder = new StringBuilder(str);

strBuilder.reverse();

return strBuilder.toString().equals(str);

}

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Very frequently asked in HCL Tech ( Based of 4 inputs )

Q25. Write a program to reverse a string iteratively and recursively ?

Core Java

Ans. Using String method -

new StringBuffer(str).reverse().toString();

Iterative -

public static String getReverseString(String str){
StringBuffer strBuffer = new StringBuffer(str.length);
for(int counter=str.length -1 ; counter>=0;counter--){
strBuffer.append(str.charAt(counter));
}
return strBuffer;
}

Recursive -

public static String getReverseString(String str){
if(str.length <= 1){
return str;
}
return (getReverseString(str.subString(1)) + str.charAt(0);
}

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Q26. What are the advantages of Hibernate ?

Hibernate

Ans. 1. No need to know SQL, RDBMS, and DB Schema.
2. Underlying Database can be changed without much effort by changing SQL dialect and DB connection.
3.Improved Performance by means of Caching.

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Q27. What is the purpose of dialect configured in Hibernate configuration file ?

Hibernate

Ans. It tells the framework which SQL varient to generate.

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Q28. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?

Database

Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.

Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count

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Q29. What is database Normalization ?

Database

Ans. https://en.wikipedia.org/wiki/Database_normalization

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Q30. Write a Program to print factorial of a number using recursion

Core Java

Ans. public class BuggyBread {
public static void main(String args[]) {
System.out.println(factorial(5));
}

private static int factorial(int number){
if(number == 1){
return 1;
} else {
return number * factorial(number - 1);
}
}
}

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Q31. What is abstraction ?

Design

Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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Q32. What are the reasons to choose between reserved and on demand instances ?

Server

Ans. In terms of compute options and configurations, Reserved Instances and On Demand instances are the same. The only difference between the two is that a Reserved Instance is one you rent (reserved) for a fixed duration, and in return you receive a discount on the base price of an On Demand instance.

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Q33. Is Google App Engine , IAAS, PAAS or SAAS ?

Google Cloud Platform (GCP)

Ans. It's PAAS ( Platform as a service )

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Q34. What is concurrent interface ?

Core Java

Ans. ConcurrentMap is an interface and it is a member of the Java Collections Framework. It represents a Map that is capable of handling concurrent access to it without affecting the consistency of entries in a map. ConcurrentMap interface present in java.util.concurrent package.

HashMap operations are not synchronized, while Hashtable provides synchronization. Though Hashtable is thread-safe, it is not very efficient. To solve this issue, the Java Collections Framework introduced ConcurrentMap in Java 1.5.

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Q35. What are system integrators in Cloud Computing?

Cloud Computing

^{This question is still unanswered. Can you please provide an answer.}

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Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes.

Q36. What is an abstract class ?

Core Java

Ans. Abstract class is the class that is not supposed to be instantiated. The purpose of the class to only have extension to the derived class.

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Q37. What are the phases of the JSP life cycle ?

Java EE

Ans. Translation of JSP PageCompilation of JSP PageClassloading (class file is loaded by the classloader)Instantiation (Object of the Generated Servlet is created).Initialization ( jspInit() method is invoked by the container).Reqeust processing ( _jspService() method is invoked by the container).Destroy ( jspDestroy() method is invoked by the container).

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Q38. What are the platforms supported by Java Programming Language?

Core Java

Ans. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX/Linux like HP-Unix, Sun Solaris, Redhat Linux, Ubuntu, CentOS, etc

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Q39. Difference between Abstraction and Implementation hiding ?

Ans. Implementation Hiding is a broader concept. Abstraction is a way of implementation hiding in OOP's.

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Q40. What is Java bytecode ?

Ans. Java bytecode is the instruction set of the Java virtual machine. Each bytecode is composed by one, or two bytes that represent the instruction, along with zero or more bytes for passing parameters.

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