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Java Generics Interview Questions

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Java Generics Interview Questions Toggle navigation In28Minutes Download Java Interview Pdf Guide Popular Video Courses Buy Java Interview Video Guide - $12.99/₹799 Start learning on Udemy today! Java Generics Interview Questions Generics Interview Questions are often used to judge the familiarity of interviewee with the latest concepts in Java. Introduced in Java 5, Generics add a unconfined deal of flexibility to Java. In this guide, we squint at important interview questions related to Generics - How to create a Generic class, method & we will discuss other important things well-nigh Generics. What are Generics? Why do we need Generics? Can you requite an example of how Generics make a program increasingly flexible? How do you declare a Generic Class? What are the restrictions in using generic type that is supposed in a matriculation declaration? How can we restrict Generics to a subclass of particular class? How can we restrict Generics to a super matriculation of particular class? Can you requite an example of a Generic Method? What are Generics? Generics are used to create Generic Classes and Generic methods which can work with variegated Types(Classes). Why do we need Generics? Can you requite an example of how Generics make a program increasingly flexible? Consider the matriculation below: matriculation MyList { private List<String> values; void add(String value) { values.add(value); } void remove(String value) { values.remove(value); } } MyList can be used to store a list of Strings only. MyList myList = new MyList(); myList.add("Value 1"); myList.add("Value 2"); To store integers, we need to create a new class. This is problem that Generics solve. Instead of hard-coding String matriculation as the only type the matriculation can work with, we make the matriculation type a parameter to the class. Example with Generics Let’s replace String with T and create a new class. Now the MyListGeneric matriculation can be used to create a list of Integers or a list of Strings matriculation MyListGeneric<T> { private List<T> values; void add(T value) { values.add(value); } void remove(T value) { values.remove(value); } T get(int index) { return values.get(index); } } MyListGeneric<String> myListString = new MyListGeneric<String>(); myListString.add("Value 1"); myListString.add("Value 2"); MyListGeneric<Integer> myListInteger = new MyListGeneric<Integer>(); myListInteger.add(1); myListInteger.add(2); How do you declare a Generic Class? Note the declaration of class:Instead of T, We can use any valid identifier. matriculation MyListGeneric<T> What are the restrictions in using generic type that is supposed in a matriculation declaration? If a generic is supposed as part of matriculation declaration, it can be used any where a type can be used in a matriculation - method (return type or argument), member variable etc. For Example: See how T is used as a parameter and return type in the matriculation MyListGeneric. How can we restrict Generics to a subclass of particular class? In MyListGeneric, Type T is specified as part of matriculation declaration. Any Java Type can be used a type for this class. If we would want to restrict the types unliable for a Generic Type, we can use a Generic Restrictions. Consider the example matriculation below: In declaration of the class, we specified a constraint "T extends Number". We can use the matriculation MyListRestricted with any matriculation extending (any sub matriculation of) Number - Float, Integer, Double etc. matriculation MyListRestricted<T extends Number> { private List<T> values; void add(T value) { values.add(value); } void remove(T value) { values.remove(value); } T get(int index) { return values.get(index); } } MyListRestricted<Integer> restrictedListInteger = new MyListRestricted<Integer>(); restrictedListInteger.add(1); restrictedListInteger.add(2); String not valid substitute for constraint "T extends Number". //MyListRestricted<String> restrictedStringList = // new MyListRestricted<String>();//COMPILER ERROR How can we restrict Generics to a super matriculation of particular class? In MyListGeneric, Type T is specified as part of matriculation declaration. Any Java Type can be used a type for this class. If we would want to restrict the types unliable for a Generic Type, we can use a Generic Restrictions. In declaration of the class, we specified a constraint "T super Number". We can use the matriculation MyListRestricted with any matriculation that is a super matriculation of Number class. Can you requite an example of a Generic Method? A generic type can be supposed as part of method declaration as well. Then the generic type can be used anywhere in the method (return type, parameter type, local or woodcut variable type). Consider the method below: static <X extends Number> X doSomething(X number){ X result = number; //do something with result return result; } The method can now be tabbed with anyMatriculationtype proffer Number. Integer i = 5; Integer k = doSomething(i); If you loved these Questions, you will love our PDF Interview Guide with 400+ Questions. 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