Quick Answer: What does

What does <? Super t mean in Java?

super T denotes an unknown type that is a supertype of T (or T itself; remember that the supertype relation is reflexive). It is the dual of the bounded wildcards we’ve been using, where we use ? extends T to denote an unknown type that is a subtype of T .

What does extends t mean in Java?

extends T> because you can’t guarantee what kind of List it is really pointing to, so you can’t guarantee that the object is allowed in that List . The only “guarantee” is that you can only read from it and you’ll get a T or subclass of T .

What does this mean <? Super T >>?

super T>> , it’s when you have something like Cat extends Animal implements Comparable<Animal> . Look at the signature of Collections.sort public static <T extends Comparable<? super T>> void sort(List<T> list) Therefore, with a List<Cat> listOfCat , you can now Collections.

What is super in Java generics?

Wildcards in Generics

A question mark, or wildcard, is used in generics to represent an unknown type. … extends Number> represents a list of Number or its sub-types such as Integer and Double. Lower Bounded Wildcards: List<? super Integer> represents a list of Integer or its super-types Number and Object.

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Why do we use super in Java?

The super keyword in Java is a reference variable that is used to refer parent class objects. The super() in Java is a reference variable that is used to refer parent class constructors. super can be used to call parent class’ variables and methods. super() can be used to call parent class’ constructors only.

Which is not a Java feature?

2) Which of the following is not a Java features? Explanation: The Java language does not support pointers; some of the major reasons are listed below: One of the major factors of not using pointers in Java is security concerns. Due to pointers, most of the users consider C-language very confusing and complex.

What is <? Super E?

When using <? super E> , it means “something in the super direction” as opposed to something in the extends direction. Example: Object is in the super direction of Number (since it is a super class) and Integer is in the extends direction (since it extends Number ).

What is Number in Java?

Java Number class is an abstract class which is placed in java. lang package. It has four abstract methods and two concrete methods. The abstract class Number is the superclass of classes BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short. This class contains a single consructor number().

What is a generic method?

Generic methods are methods that introduce their own type parameters. … Static and non-static generic methods are allowed, as well as generic class constructors. The syntax for a generic method includes a list of type parameters, inside angle brackets, which appears before the method’s return type.

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What is capture of Java?

wildcard capture is the process of binding the value of a wildcard type to a new type variable.

What is T type Java?

<T> specifically stands for generic type. According to Java Docs – A generic type is a generic class or interface that is parameterized over types.

What is difference between extends and super?

<T extends Parent> accepts either Parent or Child while <T super Parent> accepts either Parent or Grandparent.

What is Reifiable?

A reifiable type is a type whose type information is fully available at runtime. This includes primitives, non-generic types, raw types, and invocations of unbound wildcards. … A non-reifiable type does not have all of its information available at runtime.