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| Core java - Interview Questions and Answers for 'Jp morgan' - 11 question(s) found - Order By Newest | ||||
 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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 Discuss Correct / Improve  java oops string string class immutable immutability advanced  Asked in 39 Companies  expert  frequent | ||||
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| Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews. | ||||
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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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| 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) inheritance vs composition object oriented programming (oops) oops concepts Asked in 29 Companies basic frequent | ||||
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| Frequently asked at Manhattan Associates ( Based on 2 feedback ) | ||||
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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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| Discuss Correct / Improve java java8 lambda expression architecture Asked in 58 Companies expert frequent | ||||
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| Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback) | ||||
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| 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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| Discuss Correct / Improve java garbage collection java memory management advanced Asked in 21 Companies intermediate frequent | ||||
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| 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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| Discuss Correct / Improve java oop oop concepts inheritence multiple inheritence basic interview question Asked in 10 Companies basic frequent | ||||
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| Frequently asked at HCL Technologies ( Based on 3 feedback ) | ||||
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| 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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| Discuss Correct / Improve java exceptions checked exceptions unchecked exceptions exception handling checked vs unchecked exceptions Asked in 39 Companies basic frequent | ||||
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| Very frequently asked. Usually asked with questions related to String. Frequently asked at CTS / Cognizant | ||||
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| Ans. Object that can't be changed after instantiation. | ||||
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| Discuss Correct / Improve java oops immutable immutability Asked in 27 Companies basic frequent | ||||
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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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| Discuss Correct / Improve java jvm memory management permgen permanent generation advanced architecture Asked in 9 Companies expert | ||||
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| 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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| Discuss Correct / Improve check if 2 strings are Anagrams Asked in 30 Companies basic frequent | ||||
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| Ans. ClassNotFoundException is checked exception whereas NoClassDefFoundError is a unchecked exception. | ||||
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| Discuss Correct / Improve java exceptions checked exceptions unchecked exceptions exception handling Asked in 2 Companies | ||||
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| 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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| Discuss Correct / Improve threads multithreading synchronized Asked in 5 Companies basic frequent | ||||
Which of the following class creates mutable objects ?
