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| Core java - Interview Questions and Answers for 'Mit' - 13 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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| 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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| Discuss Correct / Improve oops oops features Asked in 260 Companies basic frequent | ||||
| Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews. | ||||
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| Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ). A class can extend single abstract class whereas it can implement multiple interfaces. | ||||
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| Discuss Correct / Improve java classes abstract class interfaces abstract class vs interface abstract classes vs interfaces Asked in 82 Companies basic frequent | ||||
| Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback) | ||||
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| Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not. | ||||
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| Discuss Correct / Improve java collections hashcode advanced hashtable Asked in 33 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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| 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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| 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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| Discuss Correct / Improve oops object oriented programming object oriented language primitive data types Asked in 2 Companies | ||||
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| 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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| Discuss Correct / Improve wrapper classes benefits of wrapper classes over primitives | ||||
| Usually asked to entry level software developers. | ||||
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| Ans. public static void main(String[] args) { int num1 = 1; int num2 = 2; num1 = num1^num2; num2 = num1^num2; num1 = num1^num2; System.out.print("num1 = " + num1 +", num2 = "+num2); } | ||||
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| Discuss Correct / Improve code coding Asked in 37 Companies basic frequent | ||||
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| Ans. A wrapper class is any class which "wraps" or "encapsulates" the functionality of another class or component. A Wrapper Class that wraps or encapsulates the primitive data type is called Primitive Wrapper Class. | ||||
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| Discuss Correct / Improve java wrapper classes primitive wrapper classes | ||||
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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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| Discuss Correct / Improve recursion Asked in 25 Companies | ||||
| Frequently asked in face to face interviews. | ||||
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| Ans. int count = 15; int[] fibonacci = new int[count]; fibonacci[0] = 0; fibonacci[1] = 1; for(int x=2; x < count; x++){ fibonacci[x] = fibonacci[x-1] + fibonacci[x-2]; } for(int x=0; x< count; x++){ System.out.print(fibonacci[x] + " "); } | ||||
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| Discuss Correct / Improve ebay fibonacci series Asked in 66 Companies basic frequent | ||||
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| Ans. boolean byte char double float int long short void | ||||
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| Discuss Correct / Improve data types primitive data types Asked in 1 Companies Basic | ||||
Which of the following class creates mutable objects ?
