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| Core java - Interview Questions and Answers for 'Mastercard' - 5 question(s) found - Order By Newest | ||||
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| Ans. We can make a class immutable by 1. Making all methods and variables as private. 2. Setting variables within constructor. Public Class ImmutableClass{ private int member; ImmutableClass(int var){ member=var; } } and then we can initialize the object of the class as ImmutableClass immutableObject = new ImmutableClass(5); Now all members being private , you cant change the state of the object. | ||||
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 Discuss Correct / Improve  java oops immutable immutability immutable immutability class technical lead  Asked in 5 Companies  intermediate  frequent | ||||
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 Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. | ||||
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| Ans. Final variable is a variable constant that cannot be changed after initialization. | ||||
 Sample Code for final variable | ||||
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| Discuss Correct / Improve oops java final final variable basic interview question Asked in 12 Companies basic frequent | ||||
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| Ans. Arrays.sort(numArray); double median; if (numArray.length % 2 == 0) median = ((double)numArray[numArray.length/2] (double)numArray[numArray.length/2 - 1])/2; else median = (double) numArray[numArray.length-1/2]; | ||||
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| Ans. There are four main OOP concepts in Java. These are: Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don?t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times. Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It?s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide. Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel. Polymorphism. This Java OOP concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That?s when different meanings are implied by the code itself. The other form is method overriding. That?s when the different meanings are implied by the values of the supplied variables. See more on this below. | ||||
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| Ans. The Java collections framework (JCF) is a set of classes and interfaces that implement commonly reusable collection data structures. Although referred to as a framework, it works in a manner of a library. The JCF provides both interfaces that define various collections and classes that implement them. | ||||
| Sample Code for Map Sample Code for HashMap Sample Code for Treemap Sample Code for set Sample Code for hashset Sample Code for treeset Sample Code for list Sample Code for arraylist Sample Code for linkedlist Sample Code for queue Sample Code for priorityqueue Sample Code for concurrenthashmap Sample Code for vector Sample Code for stack | ||||
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Which of the following class creates mutable objects ?
