Java Class Question Mark Extends !!

the question mark in extends declaration java makble.

in java extends declaration syntax we often see something like this public interface ruleblock t extends rule t comparable ruleblock the question mark also show up on other place inside an angle bracket it means any class its a wildcard.

java generics vs extends object baeldung.

24 12 2020 a question mark or wildcard is used in generics to represent an unknown type it can have three forms unbounded wildcards list represents a list of unknown type upper bounded wildcards list extends number represents a list of number or its sub types such as integer and double.

wildcards in java geeksforgeeks.

29 12 2016 wildcards in java the question mark is known as the wildcard in generic programming it represents an unknown type the wildcard can be used in a variety of situations such as the type of a parameter field or local variable sometimes as a return type unlike arrays different instantiations of a generic type are not compatible with.

understanding bounded generics with super and extends java.

so we know t we know the type but question mark extends t means it could be that type or it could be some child and we don t know for sure what the child type is if we are given a stack of some child type we don t know which it could be all t s it could be only some t s and so we re not going to be allowed to make an assignment add an entry.

extends vs implements in java geeksforgeeks.

22 05 2020 extends in java the extends keyword is used to indicate that the class which is being defined is derived from the base class using inheritance so basically extends keyword is used to extend the functionality of the parent class to the subclass in java multiple inheritances are not allowed due to ambiguity.

what does the question mark in java generics type parameter mean.

a question mark is a signifier for any type alone means any type extending object including object while your example above means any type extending or implementing hasword including hasword if hasword is a non abstract class.

the basics of java generics baeldung.

12 02 2020 7 conclusion java generics is a powerful addition to the java language as it makes the programmer s job easier and less error prone generics enforce type correctness at compile time and most importantly enable implementing generic algorithms without causing any extra overhead to our applications.

60 java multiple choice questions and answers 2021.

15 02 2018 java multiple choice questions 31 mark the incorrect statement from the following a java is a fully object oriented language with strong support for proper software engineering techniques b in java it is not easy to write c like so called procedural programs c in java language objects have to be manipulated.

java generics upper bounded wildcards tutorialspoint.

the question mark represents the wildcard stands for unknown type in generics there may be times when you ll want to restrict the kinds of types that are allowed to be passed to a type parameter for example a method that operates on numbers might only want to accept instances of number or its subclasses.
java class question mark extends

java class question mark extends

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