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Interview Questions and Answers for 'Orm' - 81 question(s) found - Order By Newest

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Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback )
  Q1. Difference between == and .equals() ?Core Java
Anonymous
Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory.

x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object.

Sample code:

String x = new String("str");
String y = new String("str");

System.out.println(x == y); // prints false
System.out.println(x.equals(y)); // prints true

  Sample Code for equals

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   Like         Discuss         Correct / Improve     java   string comparison   string   object class   ==    equals   object equality  operator     Asked in 289 Companies      basic        frequent

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Advanced level question. Frequently asked in High end product companies. Frequently asked in Cognizant and Deloitte ( Based on 2 feedback )
  Q2. Why is String immutable in Java ?Core Java
Anonymous
Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

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   Like         Discuss         Correct / Improve     java   oops   string   string class   immutable  immutability   advanced     Asked in 37 Companies      expert        frequent

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture.
  Q3. What is the difference between final, finally and finalize() ?Core Java
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Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing.

finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc.

finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state.

  Sample Code for final

  Sample Code for finally

  Sample Code for finalize

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   Like         Discuss         Correct / Improve     java   oops   final   finally   finalize     Asked in 60 Companies      basic        frequent

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  Q4. Explain OOPs

or

Explain OOPs Principles

or

Explain OOPs Concepts

or

Explain OOPs features

or

Tell me something about OOPs
Core Java2017-06-13 08:25:45

Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features

1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing

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   Like         Discuss         Correct / Improve     oops  oops features     Asked in 236 Companies      basic        frequent


Basic and Very Frequently asked.
  Q5. What is Polymorphism in Java ?Core Java2016-11-06 09:10:54

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

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   Like         Discuss         Correct / Improve     polymorphism  object oriented programming (oops)  oops concepts  oops concepts     Asked in 107 Companies      Basic        frequent

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  Q6. What is a String Pool ?Core Java
Anonymous
Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference.

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   Like         Discuss         Correct / Improve     java   oops   string   string class   string pool   heap memory     Asked in 31 Companies      intermediate        frequent

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Frequently asked question in companies using hibernate.
  Q7. Difference between first level and second level cache in hibernate ?Hibernate
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Ans. 1. First level cache is enabled by default whereas Second level cache needs to be enabled explicitly.

2. First level Cache came with Hibernate 1.0 whereas Second level cache came with Hibernate 3.0.

3. First level Cache is Session specific whereas Second level cache is shared by sessions that is why First level cache is considered local and second level cache is considered global.

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   Like         Discuss         Correct / Improve     hibernate   orm   hibernate cache   architecture   technical lead     Asked in 18 Companies      Intermediate        frequent


Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies.
  Q8. Difference between Overloading and Overriding ?Core Java
Anonymous
Ans. Overloading - Similar Signature but different definition , like function overloading.

Overriding - Overriding the Definition of base class in the derived class.

  Sample Code for overloading

  Sample Code for overriding

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   Like         Discuss         Correct / Improve     java   oops   overloading   overriding   oops concepts   basic interview question     Asked in 82 Companies      basic        frequent

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Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )
  Q9. What is Dependency Injection or IOC ( Inversion of Control ) ?Design

Ans. It is a Design Pattern that facilitates loose coupling by sending the dependency information ( object references of dependent object ) while building the state of the object. Objects are designed in a manner where they receive instances of the objects from other pieces of code, instead of constructing them internally and hence provide better flexibility.

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   Like         Discuss         Correct / Improve     design patterns   ioc ( Inversion of Control )  dependency injection     Asked in 80 Companies      intermediate        frequent


  Q10. Difference between Vector and ArrayList ?Core Java
Anonymous
Ans. Vectors are synchronized whereas Array lists are not.

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   Like         Discuss         Correct / Improve     java   basic interview question   vector   arraylist   collections   synchronization     Asked in 34 Companies      basic        frequent


Very frequently asked in phone and walk in interviews.
  Q11. What are Marker Interfaces ? Name few Java marker interfaces ?Core Java
Anonymous
Ans. These are the interfaces which have no declared methods.Serializable and cloneable are marker interfaces.

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   Like         Discuss         Correct / Improve     java   oops   interfaces   marker interface   serializable   clonable     Asked in 21 Companies      intermediate        frequent

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 Q12. How to configure second level cache in Hibernate ?Hibernate
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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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 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
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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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   Like         Discuss         Correct / Improve     java   db   database   hibernate   orm   at&t   overstock.com   performance improvement   architecture   technical lead   architect      intermediate


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

a. Inheritance
b. Encapsulation
c. Abstraction
d. Composition
Core Java
Anonymous
Ans. Encapsulation

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   Like         Discuss         Correct / Improve     java   java concepts   java features   oops concepts   oops features   access protection   information hiding


 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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   Like         Discuss         Correct / Improve     oops  object oriented programming  object oriented language  primitive data types     Asked in 2 Companies


This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc.
 Q16. What are the ways in which execution time of the code can be improved ?Solution2016-05-29 09:42:39

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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   Like         Discuss         Correct / Improve     performance improvement  code optimization     Asked in 1 Companies


Frequently asked to fresh graduates.
 Q17. What is ACID ?Database2016-11-04 08:09:44

Ans. ACID stands for Atomicity, Consistency, Isolation, Durability is a set of properties of database transactions.

Atomicity means all or nothing. i.e parts of a transaction shouldn't commit if any one of them fails. Either the whole transaction should succeed or it should be complete rollback.

Consistency means that any transaction should lead database from one stabe state to another.

Isolation means that the execution of transaction results in a system state that would be obtained if transactions were executed serially.

Durability means that when a transaction is committed it forms the permanent state of database.

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   Like         Discuss         Correct / Improve     database  acid     Asked in 7 Companies      Intermediate

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Frequently asked question for intermediate developers.
  Q18. What is Volatile keyword used for ?Core Java
Anonymous
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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   Like         Discuss         Correct / Improve     java   oops   synchronization   volatile   java keywords     Asked in 42 Companies      intermediate        frequent

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 Q19. What is PermGen or Permanent Generation ?Core Java
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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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   Like         Discuss         Correct / Improve     java   jvm   memory management   permgen   permanent generation   advanced   architecture     Asked in 9 Companies      expert


  Q20. Write a method to check if input String is Palindrome?Core Java
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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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   Like         Discuss         Correct / Improve     java   string   stringbuilder   stringbuilder   string class   code   palindrome     Asked in 38 Companies      Basic        frequent


Very frequently asked in HCL Tech ( Based of 4 inputs )
  Q21. Write a program to reverse a string iteratively and recursively ?Core Java
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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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   Like         Discuss         Correct / Improve     java   string   reverse   stringbuffer   string class   code     Asked in 6 Companies        frequent


 Q22. What are the advantages of Hibernate ?Hibernate
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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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 Q23. What is the purpose of dialect configured in Hibernate configuration file ?Hibernate
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Ans. It tells the framework which SQL varient to generate.

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  Q24. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?
Database2016-06-30 20:13:35

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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   Like         Discuss         Correct / Improve     sql  joins  self join  self-join  Pair of employee names with first having lesser salary than later  Pair of department names where first dept has lesser employees than the later     Asked in 26 Companies      basic        frequent


 Q25. What is the cost of using Cloud Formation ?Amazon Web Services (AWS)2019-01-08 15:53:06

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

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 Q26. Difference between AWS Cloud Formation and AWS AMI ?Amazon Web Services (AWS)2019-01-11 13:40:03

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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Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes.
  Q27. What is an abstract class ?Core Java2017-01-10 13:12:20

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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   Like         Discuss         Correct / Improve     abstract class     Asked in 6 Companies      basic        frequent


 Q28. What are the phases of the JSP life cycle ?Java EE
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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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   Like         Discuss         Correct / Improve     j2ee   servlets   servelets   web application   jsp   jsp life cycle   mindtree     Asked in 9 Companies


 Q29. What are the platforms supported by Java Programming Language?Core Java
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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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 Q30. Difference between Abstraction and Implementation hiding ?
Anonymous
Ans. Implementation Hiding is a broader concept. Abstraction is a way of implementation hiding in OOP's.

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   Like         Discuss         Correct / Improve     java   oops   oops concepts   abstraction   hiding information   build management


 Q31. What is Java bytecode ?
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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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   Like         Discuss         Correct / Improve     java   jvm   interpreter   platform independent     Asked in 1 Companies


 Q32. Is JVM a overhead ?
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Ans. Yes and No. JVM is an extra layer that translates Byte Code into Machine Code. So Comparing to languages like C, Java provides an additional layer of translating the Source Code.

C++ Compiler - Source Code --> Machine Code
Java Compiler - Source Code --> Byte Code , JVM - Byte Code --> Machine Code

Though it looks like an overhead but this additional translation allows Java to run Apps on all platforms as JVM provides the translation to the Machine code as per the underlying Operating System.


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   Like         Discuss         Correct / Improve     java   jvm   interpreter   platform independent   yes-no   advanced   architecture


 Q33. What is Byte Code ? Why Java's intermediary Code is called Byte Code ?
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Ans. Bytecode is a highly optimized set of instructions designed to be executed by the Java run-time system. Its called Byte Code because each instruction is of 1-2 bytes.

Sample instructions in Byte Code -

1: istore_1
2: iload_1
3: sipush 1000
6: if_icmpge 44
9: iconst_2
10: istore_2

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 Q34. Which of the following code is correct ?

a. DateFormat df = DateFormat.getInstance();
b. DateFormat df = DateFormat.getDateInstance();
c. DateFormat df = DateFormat.getInstance(DateFormat.FULL);
d. DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);
Core Java
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Ans. All except c are correct.

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 Q35. What is the use of parse method in DateFormat ?
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Ans. It is used to parse String to get the Date Object with initialized date.

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 Q36. Which of the following is not a valid NumberFormat initialization ?

a. NumberFormat.getInstance()
b. NumberFormat.getDateInstance()
c. NumberFormat.getCurrencyInstance()
d. NumberFormat.getNumberInstance()
Core Java
Admin
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Ans. b i.e NumberFormat.getDateInstance()

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 Q37. Which of the following code is correct ?

a. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).parse(str);

b. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).format(str);

c. Date date = DateFormat.getDateInstance(DateFormat.LONG, Locale.US).parse(str);
Core Java
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Ans. c

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 Q38. What are the the methods to clear cache in Hibernate ?Hibernate
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Ans. Evict() and clear(). Evist is used to clear a particular object from the cache whereas clear clears the complete local cache.

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 Q39. What are different types of second level cache ?Hibernate
Admin
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Ans. 1. EHCache ( Easy Hibernate )
2. OSCache ( Open Symphony )
3. Swarm Cache ( JBoss )
4. Tree Cache ( JBoss )

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 Q40. Can we disable first level cache ? What should one do if we don't want an object to be cached ?Hibernate
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Ans. No.We can either call evict after the object retrieval or can use separate sessions.

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