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Interview Questions and Answers for 'Efi' - 13 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 )
  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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Frequently asked question in companies using hibernate.
  Q2. Difference between first level and second level cache in hibernate ?Hibernate
Admin
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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


 Q3. What things should be kept in mind while creating your own exceptions in Java?Core Java
Admin
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Ans. All exceptions must be a child of Throwable.

If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.

You want to write a runtime exception, you need to extend the RuntimeException class.

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   Like         Discuss         Correct / Improve     java   exceptions   exception handling   user defined exceptions   throwable   architecture   library development   technical architect   technical lead


 Q4. What are the benefits of using Wrapper classes over primitive types ?Core Java2017-08-24 21:35:53

Ans. With Collection classes , we cannot use primitive types. Moreover for any class using generic types, we cannot use primitive types.

They add more functionality by means of additional methods.

As their reference can be null , they offer consistent check for uninitialized state.

They facilitate caching and reuse by means of constant Pools.

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   Like         Discuss         Correct / Improve     wrapper classes  benefits of wrapper classes over primitives


 Q5. What is DTD ?Xml
Admin
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Ans. DTD or Document Type Definition is a standard agreed upon way of communication between two parties. Your application can use a standard DTD to verify that data that you receive
from the outside world is valid and can be parsed by your parser.

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   Like         Discuss         Correct / Improve     xml   markup language   dtd   document type definition   architecture


 Q6. What are few of the Annotations pre defined by Java?
Anonymous
Ans. @Deprecated annotation indicates that the marked element is deprecated and should no longer be used. The compiler generates a warning whenever a program uses a method, class, or field with the @Deprecated annotation.

@Override annotation informs the compiler that the element is meant to override an element declared in a superclass.

@SuppressWarnings annotation tells the compiler to suppress specific warnings that it would otherwise generate.

@SafeVarargs annotation, when applied to a method or constructor, asserts that the code does not perform potentially unsafe operations on its varargsparameter. When this annotation type is used, unchecked warnings relating to varargs usage are suppressed.

@FunctionalInterface annotation, introduced in Java SE 8, indicates that the type declaration is intended to be a functional interface, as defined by the Java Language Specification.

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   Like         Discuss         Correct / Improve     java   java8   annotations   pre defined annotations


Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q7. Explain Singleton Design Pattern ?Design
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Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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   Like         Discuss         Correct / Improve     java   design pattern   singleton   at&t   ebay  fidelity india  united healthcare india     Asked in 46 Companies      intermediate        frequent


 Q8. Difference between prefix and postfix increment operator ?
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Ans. Prefix operator performs the increment and then assignment whereas its inverse for postfix operator.

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   Like         Discuss         Correct / Improve     prefix increment operator   postfix increment operator   operators   java      basic        frequent


Frequently asked in high end product companies.
 Q9. Write code for LRU CacheCore Java2017-01-10 10:15:17

Ans. https://www.geeksforgeeks.org/lru-cache-implementation/

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   Like         Discuss         Correct / Improve     cache  LRU cache  coding  code     Asked in 10 Companies      intermediate


  Q10. What are the core OOPs concepts ?Core Java2017-02-06 16:15:55

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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   Like         Discuss         Correct / Improve     core oops concepts     Asked in 65 Companies      basic        frequent


 Q11. What are the benefits of using Prepared statements ?Database2017-03-09 11:32:07

Ans. 1. Precompilation , DB-side caching and reuse of same execution plan leads to overall faster execution.

2. Automatic prevention of SQL injection attacks by escaping special characters

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   Like         Discuss         Correct / Improve     Prepared statements  benefits of prepared statements     Asked in 1 Companies

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 Q12. What are the benefits of using prepared statements ? Does that benefit extend only if similar prepared statements are used within a application or it extends even with multiple applications having similar prepared statement ?Database2017-03-09 11:33:25

Ans. Prepared Statements helps in reuse of database execution plan which can be cached at Database level and hence helps achieving faster execution and performance. As cached ps objects are creating at Database level and not application level, the use and benefit extends across multiple applications.

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   Like         Discuss         Correct / Improve     Prepared statements  benefits of prepared statements     Asked in 1 Companies

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 Q13. What are the benefits of immutability or Immutable classes ?Core Java2017-08-28 19:36:18

Ans. Immutable objects are thread-safe so you will not have any synchronization issues.Immutable objects are good for Map keys and Set elements, since these typically do not change once created.Immutability makes it easier to write, use and reason about the code (class invariant is established once and then unchanged)Immutability makes it easier to parallelize your program as there are no conflicts among objects.The internal state of your program will be consistent even if you have exceptions.References to immutable objects can be cached as they are not going to change.

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   Like         Discuss         Correct / Improve     immutable  immutability classes   benefits of immutable  immutability classes     Asked in 1 Companies




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