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Interview Questions and Answers for 'Jp morgan' - 22 question(s) found - Order By Newest

Advanced level question. Frequently asked in High end product companies. Frequently asked in Cognizant and Deloitte ( Based on 2 feedback )
  Q1. 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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Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews.
  Q2. What are the difference between composition and inheritance in Java?Core Java
Admin
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Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.

Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.

Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism

Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.

Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.

  Sample Code for inheritance

  Sample Code for composition

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   Like         Discuss         Correct / Improve     java   java concepts   inheritance  object oriented programming (oops)  oops concepts   composition  object oriented programming (oops)  oops concepts   inheritance  object oriented programming (oops)  oops concepts vs composition  object oriented programming (oops)  oops concepts     Asked in 28 Companies      basic        frequent

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  Q3. What is a Lambda Expression ? What's its use ?Core Java
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Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

  Sample Code for lambda

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   Like         Discuss         Correct / Improve     java   java8   lambda expression   architecture     Asked in 57 Companies      expert        frequent

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Frequently asked question in companies using hibernate.
  Q4. 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


Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback)
  Q5. Describe, in general, how java's garbage collector works ?Core Java
Anonymous
Ans. The Java runtime environment deletes objects when it determines that they are no longer being used. This process is known as garbage collection. The Java runtime environment supports a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector that scans Java dynamic memory areas for objects, marking those that are referenced. After all possible paths to objects are investigated, those objects that are not marked (i.e. are not referenced) are known to be garbage and are collected.

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   Like         Discuss         Correct / Improve     java   garbage collection   java memory management   advanced     Asked in 21 Companies      intermediate        frequent

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  Q6. Does Java support Multiple Inheritance ?Core Java
Anonymous
Ans. Java doesn't support multiple inheritance. Interfaces does't facilitate inheritance and hence implementation of multiple interfaces doesn't make multiple inheritance.

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   Like         Discuss         Correct / Improve     java   oop   oop concepts   inheritence   multiple inheritence   basic interview question     Asked in 8 Companies      basic        frequent

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Very frequently asked. Usually asked with questions related to String.
  Q7. What is an Immutable Object ?Core Java
Anonymous
Ans. Object that can't be changed after instantiation.

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   Like         Discuss         Correct / Improve     java   oops   immutable  immutability     Asked in 27 Companies      basic        frequent

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 Q8. 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


Frequently asked at HCL Technologies ( Based on 3 feedback )
  Q9. Difference between Checked and Unchecked exceptions ?Core Java
Anonymous
Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.

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   Like         Discuss         Correct / Improve     java   exceptions   checked exceptions   unchecked exceptions   exception handling   basic interview question     Asked in 37 Companies      basic        frequent

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 Q10. Give an Example of checked and unchecked exception ?Core Java
Anonymous
Ans. ClassNotFoundException is checked exception whereas NoClassDefFoundError is a unchecked exception.

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   Like         Discuss         Correct / Improve     java   exceptions   checked exceptions   unchecked exceptions   exception handling     Asked in 2 Companies


Usually asked only to fresh graduates and less experienced developers.
  Q11. What is a daemon thread? Give an Example ?
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Ans. These are threads that normally run at a low priority and provide a basic service to a program or programs when activity on a machine is reduced. garbage collector thread is daemon thread.

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   Like         Discuss         Correct / Improve     java   threads   multi threading   operating system   daemon thread   garbage collection     Asked in 10 Companies      intermediate        frequent

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  Q12. Write a Program to check if 2 strings are Anagrams ?Core Java2016-11-30 20:52:37

Ans. public void checkIfAnagram(String str1,String str2){
boolean anagram = true;
for(char c:str1.toCharArray()){
if(!str2.contains(String.valueOf(c))){
System.out.println("Strings are Anagrams");
anagram = false;
}

if(anagram == true){
System.out.println("Strings are not Anagrams");
}
}
}

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   Like         Discuss         Correct / Improve      check if 2 strings are Anagrams     Asked in 29 Companies      basic        frequent


 Q13. Difference between Assert and Verify ?Testing
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Ans. Assert works only if assertions ( -ea ) are enabled which is not required for Verify.Assert throws an exception and hence doesn't continue with the test if assert evaluates to false whereas it's not so with Verify.

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   Like         Discuss         Correct / Improve     assert   junit   mockito   verify   testing   unit testing     Asked in 5 Companies


Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q14. 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


 Q15. What is a BlockingQueue?Data Structures
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Ans. BlockingQueue is a Queue that supports operations that wait for the queue to become non-empty when retrieving and removing an element, and wait for space to become available in the queue when adding an element.

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   Like         Discuss         Correct / Improve     blockingqueue   collections   java   concurrent collections     Asked in 10 Companies


 Q16. What is CRUD ?Database2016-06-13 10:34:03

Ans. CRUD stands for "Create, read, update and delete" are the basic functions of persistence.

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   Like         Discuss         Correct / Improve     CRUD  Persistence  Database  Database Operations     Asked in 3 Companies      Basic        frequent


Frequently asked for Lead and Architect positions. Recently asked in many US companies.
  Q17. What are Anti Patterns ?Design2016-07-14 14:21:11

Ans. Anti-pattern is simply the creation of a pattern in your coding that negatively affects your code i.e the Negatives surpasses the positives.

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   Like         Discuss         Correct / Improve     anti patterns  design patterns     Asked in 9 Companies        frequent


 Q18. What are design situations to use Singleton and Prototype Design Pattern ?Design2016-07-28 20:28:43

Ans. Both are creational design patterns.

Singleton is used when we would like to reuse an object if object is not supposed to hold request or thread specific information. Inversely Prototype is used in situations where we would like to reuse the object information but the request / thread may require it own data to be persisted.

In short, Singleton is used in situations where we can live with single object being shared across multiple requests or threads whereas Prototype is used when we need duplicate copies of objects.

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   Like         Discuss         Correct / Improve     design pattern  singleton  prototype  creational design pattrn     Asked in 7 Companies      expert

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Very frequently asked.
 Q19. What is the use of synchronized keyword ?Core Java2016-11-04 08:15:53

Ans. Synchronize is used to achieve mutual exclusion i.e at one time, the segment of the code, method that has been declared synchronized should be executed by single thread only and hence the lock needs to be retrieved before executing the segment and then released.

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   Like         Discuss         Correct / Improve     threads  multithreading  synchronized     Asked in 5 Companies      basic        frequent


Frequently asked in Accenture.
  Q20. What is your biggest achievement at work ?General2016-12-15 14:14:22

Ans. [Open Ended Answer]

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   Like         Discuss         Correct / Improve     general question  non technical question     Asked in 20 Companies        frequent


 Q21. What is Spring Boot ?Spring Boot2016-12-19 06:23:21

Ans. Spring Boot is Springs convention-over-configuration solution for creating stand-alone, production-grade Spring-based Applications.

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   Like         Discuss         Correct / Improve     Spring Boot     Asked in 7 Companies


 Q22. How to parse nested json object ?JSON2019-01-04 10:12:48

Ans. JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");

for (Map.Entry in jsonChildOBject.entrySet()) {
System.out.println("Key = " entry.getKey() ", Value = " entry.getValue());
}

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   Like         Discuss         Correct / Improve     json  nested json     Asked in 1 Companies




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