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Interview Questions and Answers for 'ORM' - 110 question(s) found - Order By Newest | ||||
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 ) and Epam Systems | ||||
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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   == vs equals   equals vs == Asked in 294 Companies basic   frequent | ||||
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Advanced level question. Frequently asked in High end product companies. Frequently asked in Google , Cognizant and Deloitte ( Based on 2 feedback ) | ||||
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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 39 Companies expert   frequent | ||||
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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 260 Companies basic   frequent | ||||
Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture. | ||||
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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   final vs finally vs finalize Asked in 61 Companies basic   frequent | ||||
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Basic and Very Frequently asked. | ||||
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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 108 Companies Basic   frequent | ||||
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Frequently asked in Infosys India | ||||
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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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Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies. | ||||
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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   overloading vs overriding Asked in 86 Companies basic   frequent | ||||
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Frequently asked question in companies using 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   first level cache vs second level cache Asked in 18 Companies Intermediate   frequent | ||||
Frequently asked to fresh graduates. | ||||
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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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Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc ) | ||||
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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 83 Companies intermediate   frequent | ||||
Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM. | ||||
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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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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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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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Ans. Encapsulation | ||||
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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 | ||||
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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   vector vs arraylist Asked in 35 Companies basic   frequent | ||||
Very frequently asked in phone and walk in interviews. | ||||
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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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Like Discuss Correct / Improve  java   oops   interfaces   marker interface   serializable   clonable Asked in 21 Companies intermediate   frequent | ||||
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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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This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc. | ||||
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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 | ||||
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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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Ans. Cloud Formation does not have any additional cost but you are charged for the underlying resources it builds. | ||||
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Ans. Because it gives the ability to provision infrastructure on Demand with No contracts and strings attached. | ||||
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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 | ||||
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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 ) | ||||
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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 | ||||
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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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Ans. It tells the framework which SQL varient to generate. | ||||
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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 | ||||
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Ans. https://en.wikipedia.org/wiki/Database_normalization | ||||
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Like Discuss Correct / Improve  normalization  database Asked in 35 Companies intermediate   frequent | ||||
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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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Like Discuss Correct / Improve  recursion Asked in 25 Companies | ||||