Chapter 9: Inheritance and Interfaces
Inheritance Hierarchies. ? Implementing Subclasses. ? Overriding Methods. ? Polymorphism. ? Object: The Cosmic Superclass. ? Interface Types
Unit 2 Inheritance Packages and Interfaces Dr. Suresh Yadlapati
https://www.pvpsiddhartha.ac.in/dep_it/lecture%20notes/JAVA19/Unit%202.pdf
INHERITANCE AND INTERFACES UNIT -2
INHERITANCE AND INTERFACES. 2.1 InherItance. Inheritance is the mechanism in java by which one class is allow to inherit the features.
CS200: Advanced OO in Java interfaces inheritance
https://www.cs.colostate.edu/~cs200/Spring16/slides/08-advOO.pdf
Efficient Implementation of Java Interfaces: Invokeinterface
thod table dispatch does not handle multiple inheritance and interfaces. This complication has led to a widespread misimpression that interface method
UNIT -IV INHERITANCE PACKAGES AND INTERFACES
package. 4.3Defining interface inheritance on interfaces
Java - Inheritance/Polymorphism/Interface Reusing Classes in Java
Java - Inheritance/Polymorphism/Interface. CS 4354. Fall 2012. Jill Seaman. 1. Reusing Classes in Java. • Composition. ?A new class is composed of object
Java - Inheritance/Polymorphism/Interfaces Interface 3 definitions
Java - Inheritance/Polymorphism/Interfaces. Horstmann chapters 4.1-5 & 6.1. CS 4354. Summer II 2016. Jill Seaman. 1. Interface 3 definitions used in this
Better Object Oriented Paradigm Inheritance and Interface through
propagate the difference between using object oriented class inheritance and interfaces in C# source code using cohesion measures by metrics.
Difference Between Inheritance and Interface in Java Key Difference
29 Dec 2017 and an interface is to implement abstract classes and multiple inheritance. What is Inheritance in Java? Inheritance can achieve code re ...
ADVANCED JAVA - Princeton University
Feb 10 2021 · Inheritance overview Implementation inheritance (subclassing) ?Define a new class (subclass) from another class (base class or superclass) ?The subclass inherits from the base class: instance variables (state) instance methods (behavior) ?The subclass can override instance methods in the base class (replacing with own versions) Main benefits
Interface and Inheritance in Java: Inheritance
Java has two mechanisms for inheritance: 1 Interface using implements keyword; methods only 2 Class using extends keyword; methods and variables Composition - allows a new class to specify other existing classes that are a part of it In Java composition simply means that one object is a member variable of another
Java Inheritance Interfaces - College of Computing & Informatics
Java – Inheritance Interfaces Kurt Schmidt Intro Java Classes Inheritance Casting Containers Interfaces Exceptions Nested Classes Containers and Interfaces Instances of an class implementing an interface can be viewed as objects of that type A KeyListener object whatever else it is has methods keyTyped keyPressed and keyReleased
Inheritance and Interfaces
Java API Swingsort usesapplication-specific code Inheritance terminology: a subclass (or derivedclass) inherits from a superclass (or baseclass) subclass class is a specializationof the superclass add or change functionality reuse code and interface can use subclass objects in place of superclaobjects
Java – Generics Interface and Inheritance
A Java interface is a collection of abstract methods and constants An abstract method is a method header without a method body An abstract method can be declared using the modifier abstract but because all methods in an interface are abstract usually it is left off An interface is used to establish a set of
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Java Interface • Method Prototypes - An interface defines a set of method prototypes - Does not provide code for implementation -- just the prototypes - Can also define final constants • Class implements interface - A class that implements an interface must implement all the methods in the interface The compiler
[PDF] Unit 2 Inheritance Packages and Interfaces Dr Suresh Yadlapati M
Inheritance Packages and Interfaces Inheritance can be defined as the process where one class acquires the properties of another class
[PDF] INHERITANCE AND INTERFACES UNIT -2
Inheritance is the mechanism in java by which one class is allow to inherit the features (fields and methods) of another class It is process of deriving a new
[PDF] Chapter 9: Inheritance and Interfaces
A Java interface type declares a set of methods and their signatures Page 56 Syntax 9 4: Interface Types ? An interface declaration and a class that
[PDF] UNIT -IV INHERITANCE PACKAGES AND INTERFACES
? Inheritance provides reusability of code ? Java class can be reused in several ways by creating new class ? Reusing the properties of existing
[PDF] Inheritance in Java - WordPresscom
Inheritance in java is a mechanism in which one object acquires all the properties and behaviors of parent object • The idea behind inheritance in java is
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In java programming multiple and hybrid inheritance is supported through interface only We will learn about interfaces later Page 4 Note: Multiple
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It is used to achieve abstraction and multiple inheritance in Java In other words you can say that interfaces can have abstract methods and variables It
[PDF] Java - Inheritance/Polymorphism/Interface
Java - Inheritance/Polymorphism/Interface CS 4354 Fall 2012 Jill Seaman 1 Reusing Classes in Java • Composition ?A new class is composed of object
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The implements keyword is used by classes by inherit from interfaces Interfaces can never be extended by the classes Example: public interface Animal {}
[PDF] Java Classes Objects Inheritance Abstract and Interfaces Recap 2
the same type A Java class uses: variables to define data fields and methods to define behaviors
What is inheritance in Java?
- In other words every class in java directly or indirectly inherits Object class. By means of inheritance a class gets all the public, protected properties and methods of the super class no matter which package the sub class is present in.
How to use multiple inheritance using interfaces in Java?
- Here is the complete java program example of multiple inheritance using interfaces. Also, it will extend one class as extending one class in java is allowed. In this java program, Bird class will extend one class (Color) and use multiple inheritance properties by implementing 2 interfaces i.e. IFlyable and IEatable
What is implementation inheritance (subclassing)?
- 4 Implementation inheritance (subclassing). ?Define a new class (subclass) from another class (base class or superclass). ?The subclass inherits from the base class: – instance variables (state) – instance methods (behavior) ?The subclass can override instance methods in the base class (replacing with own versions).
Can we implement iterators in Java?
- Two Java interfaces that allow a client to iterate over items in a collection without exposing its internal representation. This course. ?Yes: use iterators in client code. ?Yes: implement iterators (Assignment 2 only). 35 Stack stack = new Stack(); ... for (String s : stack) { ... © Copyright 2021 Robert Sedgewick and Kevin Wayne 36
SEEM 3460 1SEEM 3460 11
Java - Generics, Interface, and
Inheritance
SEEM 3460 2
The ArrayList Class
The ArrayListclass is part of the java.util
packageLike an array, it can store a list of values and
reference each one using a numeric indexHowever, you cannot use the bracket syntax
with an ArrayListobjectFurthermore, an ArrayListobject grows and
shrinks as needed, adjusting its capacity as necessarySEEM 3460 3
The ArrayList Class
An ArrayListobject is created as follows:
ArrayList band = new ArrayList();
A list of methods supported by ArrayListclass is
given in Chapter 7 of the text book. Some examples of methods: void add(int index, Object obj)Object get(int index)
Elements can be inserted or removed with a single method invocation. For example: band.add(2,"Paul"); bandMember = band.get(1);SEEM 3460 4
The ArrayList Class
When an element is inserted, the other elements "move aside" to make roomLikewise, when an element is removed, the
list "collapses" to close the gapThe indexes of the elements adjust
accordinglySEEM 3460 5
The ArrayList Class
An ArrayListstores references to the Object
class, which allows it to store any kind of objectWe can also define an ArrayListobject to
accept a particular type of objectThe following declaration creates an ArrayList
object that only stores FamilyobjectsThis is an example of generics and we can call
ArrayLista generic type
ArrayListSEEM 3460 6
ArrayList Efficiency
The ArrayListclass is implemented using an
underlying arrayThe array is manipulated so that indexes remain
continuous as elements are added or removedIf elements are added to and removed from the
end of the list, this processing is fairly efficientBut as elements are inserted and removed from
the front or middle of the list, the remaining elements are shiftedSEEM 3460 7
Collection Classes
The Java standard library contains several
classes that represent collections, often referred to as the Java Collections APITheir underlying implementation is implied in
the class names such as ArrayListandLinkedList
The classes are implemented as generic types
It means that the type of object can be
established when an object of that collection type is instantiated.SEEM 3460 8
Generic Types
A class can be defined to operate on a generic
data type which is specified when the class is instantiated:LinkedList myList = new LinkedList();
By specifying the type stored in a collection, only objects of that type can be added to it Furthermore, when an object is removed, its type
is already establishedSEEM 3460 9SEEM 3460 9
Interfaces
A Java interfaceis a collection of abstract
methods and constantsAn abstract methodis a method header without
a method bodyAn abstract method can be declared using the
modifier abstract, but because all methods in an interface are abstract, usually it is left offAn interface is used to establish a set of
methods that a class will implementSEEM 3460 10SEEM 3460 10
Interfaces
public interface Doable public void doThis(); public int doThat(); public void doThis2 (float value, char ch); public boolean doTheOther (int num); }interfaceis a reserved wordNone of the methods in
an interface are given a definition (body)A semicolon immediately
follows each method headerSEEM 3460 11SEEM 3460 11
Interfaces
An interface cannot be instantiated
Methods in an interface have public visibility by
defaultA class formally implements an interface by:
stating so in the class header providing implementations for each abstract method in the interface If a class asserts that it implements an interface, it mustdefine all methods in the interfaceSEEM 3460 12SEEM 3460 12
Interfaces
public class CanDo implements Doable public void doThis () // whatever public void doThat () // whatever // etc. }implementsis a reserved wordEach method listed
inDoableis given a definitionSEEM 3460 13SEEM 3460 13
Interfaces
A class that implements an interface can
implement other methods as well See Complexity.javaSee Question.javaSee MiniQuiz.javaIn addition to (or instead of) abstract methods,
an interface can contain constantsWhen a class implements an interface, it gains
access to all its constantsSEEM 3460 14SEEM 3460 14SEEM 3460 14
// Complexity.java // Represents the interface for an object that can be assigned an // explicit complexity. public interface Complexity public void setComplexity (int complexity); public int getComplexity();SEEM 3460 15SEEM 3460 15SEEM 3460 15
// Question.java // Represents a question (and its answer). public class Question implements Complexity private String question, answer; private int complexityLevel; // Constructor: Sets up the question with a default complexity. public Question (String query, String result) question = query; answer = result; complexityLevel = 1; // Sets the complexity level for this question. public void setComplexity (int level) complexityLevel = level;SEEM 3460 16SEEM 3460 16SEEM 3460 16
// Returns the complexity level for this question. public int getComplexity() return complexityLevel; // Returns the question. public String getQuestion() return question; // Returns the answer to this question. public String getAnswer() return answer;SEEM 3460 17SEEM 3460 17SEEM 3460 17
// Returns true if the candidate answer matches the answer. public boolean answerCorrect (String candidateAnswer) return answer.equals(candidateAnswer); // Returns this question (and its answer) as a string. public String toString() return question + "\n" + answer;SEEM 3460 18SEEM 3460 18SEEM 3460 18
// MiniQuiz.java // Demonstrates the use of a class that implements an interface. import java.util.Scanner; public class MiniQuiz // Presents a short quiz. public static void main (String[] args)Question q1, q2;
String possible;
Scanner scan = new Scanner (System.in);
q1 = new Question ("What is the capital of Jamaica?", "Kingston"); q1.setComplexity (4); q2 = new Question ("Which is worse, ignorance or apathy?", "I don't know and I don't care"); q2.setComplexity (10);SEEM 3460 19SEEM 3460 19SEEM 3460 19
System.out.print (q1.getQuestion());
System.out.println (" (Level: " + q1.getComplexity() + ")"); possible = scan.nextLine(); if (q1.answerCorrect(possible))System.out.println ("Correct");
else System.out.println ("No, the answer is " + q1.getAnswer());System.out.println();
System.out.print (q2.getQuestion());
System.out.println (" (Level: " + q2.getComplexity() + ")"); possible = scan.nextLine(); if (q2.answerCorrect(possible))System.out.println ("Correct");
else System.out.println ("No, the answer is " + q2.getAnswer());SEEM 3460 20SEEM 3460 20SEEM 3460 20
MiniQuiz.java - Sample Execution
The following is a sample execution of
MiniQuiz.class
cuse93> java MiniQuizWhat is the capital of Jamaica? (Level: 4)Kingston
Correct
Which is worse, ignorance or apathy? (Level: 10)
sorry i dont knowNo, the answer is I don't know and I don't care
SEEM 3460 21SEEM 3460 21
Interfaces
A class can implement multiple interfaces
The interfaces are listed in the implements
clauseThe class must implement all methods in all
interfaces listed in the header class ManyThings implements interface1, interface2 // all methods of both interfacesSEEM 3460 22SEEM 3460 22
Interfaces
The Java standard class library contains
many helpful interfacesThe Comparableinterface contains one
abstract method called compareTo, which is used to compare two objectsThe Stringclass implements
Comparable, giving us the ability to put
strings in lexicographic orderSEEM 3460 23SEEM 3460 23
The Comparable Interface
Any class can implement Comparableto provide a
mechanism for comparing objects of that type if (obj1.compareTo(obj2) < 0)System.out.println ("obj1 is less than obj2");
The value returned from compareToshould be negative is obj1is less that obj2, 0 if they are equal, and positive if obj1is greater than obj2 When a programmer designs a class that implements theComparableinterface, it should follow this intent
SEEM 3460 24SEEM 3460 24
The Comparable Interface
It's up to the programmer to determine what
makes one object less than anotherFor example, you may define the compareTo
method of an Employeeclass to order employees by name (alphabetically) or by employee numberThe implementation of the method can be as
straightforward or as complex as needed for the situationSEEM 3460 25SEEM 3460 25
Interfaces
You could write a class that implements certain
methods (such as compareTo) without formally implementing the interface (Comparable)However, formally establishing the relationship
between a class and an interface allows Java to deal with an object in certain waysInterfaces are a key aspect of object-oriented
design in JavaSEEM 3460 26SEEM 3460 26
Inheritance
Inheritanceallows a software developer to derive
a new class from an existing oneThe existing class is called the parent class,or
superclass, or base classThe derived class is called the child classor
subclassAs the name implies, the child inherits
characteristics of the parentThat is, the child class inherits the methods and
data defined by the parent classSEEM 3460 27SEEM 3460 27
Inheritance
Inheritance relationships are shown in a UML class diagram using a solid arrow with an unfilled triangular arrowhead pointing to the parent class &DU •Proper inheritance creates an is-arelationship, meaning the child is amore specific version of the parentSEEM 3460 28SEEM 3460 28
Inheritance
A programmer can tailor a derived class as
needed by adding new variables or methods, or by modifying the inherited onesSoftware reuseis a fundamental benefit of
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