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OOP: Abstraction
1 parent e4a1983 commit bcb8a67

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‎objectorientedprogramming/abstraction/AbstractWithFinal.java‎

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/**
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* final and abstract cannot be used together.
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* WARNING:
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* Compile time error due to final abstract class and final abstract method.
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*
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* @author L.Gobinath
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*/
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public final abstract class AbstractWithFinal {
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public final abstract void doStuff();
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}

‎objectorientedprogramming/abstraction/AbstractWithPrivate.java‎

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/**
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* private and abstract cannot be used together.
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* WARNING:
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* Compile time error due to private abstract method.
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*
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* @author L.Gobinath
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*/
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public abstract class AbstractWithPrivate {
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private abstract void doStuff();
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}

‎objectorientedprogramming/abstraction/AbstractWithStatic.java‎

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/**
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* static and abstract cannot be used together.
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* WARNING:
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* Compile time error due to static abstract method.
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*
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* @author L.Gobinath
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*/
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public abstract class AbstractWithStatic {
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public static abstract void doStuff();
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}

‎objectorientedprogramming/abstraction/BankAccountDemo.java‎

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/**
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* Sample project to explain the abstraction.
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* The abstract sub classes can decide on overriding.
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* If an abstract class overrides any abstract methods of their super class,
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* upcomping sub classes do not need to override those methods.
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*
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* @author L.Gobinath
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*/
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public class BankAccountDemo {
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public static void main(String[] args) {
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doStuff(new ChildrensSavingsAccount());
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doStuff(new GeneralSavingsAccount());
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doStuff(new CurrentAccount());
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}
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public static void doStuff(Account acc) {
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System.out.println("Account name: " + acc.getName());
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System.out.println("Is cheque available: " + acc.isChequeAvailable());
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acc.interest();
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}
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}
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/**
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* Abstract class Account with two abstract methods.
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*/
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abstract class Account {
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/**
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* Abstract method.
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*/
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public abstract void interest();
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/**
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* Abstract method.
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*/
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public abstract boolean isChequeAvailable();
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/**
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* Non-abstract method.
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* An abstract class can have any number of non-abstract methods.
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* @return The name of the account
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*/
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public String getName() {
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String accName = this.getClass().toString().replace("class ", "");
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return accName;
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}
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}
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/**
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* Abstract sub class of Account.
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* Overrides only one abstract method: isChequeAvailable.
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* Sub classes do not need to override isChequeAvailable.
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*/
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abstract class SavingsAccount extends Account {
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@Override
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public boolean isChequeAvailable() {
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return false;
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}
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}
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/**
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* Non-abstract sub class of SavingsAccount.
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* No need to override isChequeAvailable.
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* Must override the abstract method interest.
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*/
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class ChildrensSavingsAccount extends SavingsAccount {
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@Override
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public void interest() {
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System.out.println("Interest: 5.0%");
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}
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}
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/**
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* Non-abstract sub class of SavingsAccount.
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* No need to override isChequeAvailable.
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* Must override the abstract method interest.
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*/
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class GeneralSavingsAccount extends SavingsAccount {
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@Override
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public void interest() {
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System.out.println("Interest: 4.0%");
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}
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}
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/**
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* Non-abstract sub class of Account.
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* It must override both interest and isChequeAvailable.
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*/
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class CurrentAccount extends Account {
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@Override
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public void interest() {
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System.out.println("No interest");
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}
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@Override
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public boolean isChequeAvailable() {
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return true;
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}
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}

‎objectorientedprogramming/abstraction/DoctorDemo.java‎

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/**
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* Sample code used to explain Object Oriented Programming.
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* 1.0 - The orginal source code.
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* 1.1 - All the properties of Animals have been encapsulated.
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* 1.2 - Inheritance is applied by introducing a super class Animal.
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* 1.3 - The treatment logic has been moved to the Animals.
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*
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* @version 1.3
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* @author L.Gobinath
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*/
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public class DoctorDemo {
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public static void main(String[] args) {
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Cat cat = new Cat();
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Dog dog = new Dog();
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VeterinaryDoctor doctor = new VeterinaryDoctor();
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cat.setAge(4);
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dog.setAge(2);
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doctor.giveTreatment(cat);
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doctor.giveTreatment(dog);
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}
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}
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class VeterinaryDoctor {
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/**
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* Give treatment to any Animals.
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* @param animal The animal.
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*/
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public void giveTreatment(Animal animal) {
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animal.treatment();
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}
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}
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/**
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* Super class Animal.
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*/
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class Animal {
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private int age;
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public int getAge() {
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return this.age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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public void treatment() {
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}
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}
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class Cat extends Animal {
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@Override
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public void treatment() {
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if (getAge() < 3) {
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System.out.println("Treatment C1");
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} else {
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System.out.println("Treatment C2");
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}
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}
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}
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class Dog extends Animal {
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@Override
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public void treatment() {
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if (getAge() < 5) {
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System.out.println("Treatment D1");
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} else {
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System.out.println("Treatment D2");
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}
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}
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}

‎objectorientedprogramming/abstraction/v1/Car.java‎

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/**
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* Sample Car class.
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*
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* @version 1.0
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* @author L.Gobinath
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*/
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public class Car {
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public void drive() {
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System.out.println("Use steering wheel");
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}
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}

‎objectorientedprogramming/abstraction/v1/Motorbike.java‎

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/**
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* Sample Motorbike class.
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*
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* @version 1.0
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* @author L.Gobinath
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*/
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public class Motorbike {
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public void drive() {
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System.out.println("Use handlebars");
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}
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}

‎objectorientedprogramming/abstraction/v1/Vehicle.java‎

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/**
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* Sample abstract Vehicle class.
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*
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* @version 1.0
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* @author L.Gobinath
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*/
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public abstract class Vehicle {
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/**
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* Implementation of drive method is unknown for Vehicle.
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* Notice that the method is terminated with a semicolon.
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*/
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public abstract void drive();
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}

‎objectorientedprogramming/abstraction/v1/VehicleDemo.java‎

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/**
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* Testing class for Vehicle class.
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* WARNING:
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* This class gives compile time error.
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* Cannot instantiate the abstract class.
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*
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* @version 1.0
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* @author L.Gobinath
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*/
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public class VehicleDemo {
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public static void main(String[] args) {
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Vehicle vehicle = new Vehicle(); // Compile time error
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}
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}

‎objectorientedprogramming/abstraction/v2/Car.java‎

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/**
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* Car class is a subclass of Vehicle.
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*
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* @version 2.0
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* @author L.Gobinath
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*/
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public class Car extends Vehicle {
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/**
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* Car class is a non-abstract sub class of Vehicle.
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* Must override the drive method.
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*/
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public void drive() {
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System.out.println("Use steering wheel");
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}
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}

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