Question

Explain the following object-oriented(OO) concepts with the aid of code examples (either C++ or Java): Inheritance Over-riding . Over-loading Describe any differences between C++ and Java in how these OO concepts are implemented? 3(c) 17 Marks] Describe C++ namespaces using a code example. Describe Java packages, again using a code example. How do C++ namespaces compare to Java packages? 3(d) [5 Marks] What are inline methods in C++/Java? Explain the terms accessor and mutator.

Answer 1

Inheritance :

Inheritance is one of the best feature or concept in which child class (Derived (c++)/sub class(Java)) accesses the
properties of parent class (Base(c++)/Super class(Java)) .

In java There are 3 type of inheritance while in C++ it has 5 types.

C++ :

Single Inheritance : One Base class & One Derived class
Multilevel Inheritance : One base class ,One derived class & again sub derived class and so on
Hierarchical Inheritance : One base and multiple derived classes
Multiple Inheritance : Multiple Base classes but single child class
Hybrid Inheritance : a combination of two ineritances like a combination of hierarchical and multiple inheritance

Java :

Single Inheritance : One super class & One sub class
Multilevel Inheritance : One super class ,One sub class & again subclass has sub class and so on
Hierarchical Inheritance : One super class and multiple sub classes

Java has only three types because in java a child has only one parent means Multiple parents are not allowed in java

Example of Inheritance in java :

Two classes Employee(Super class) & Manager (Sub class)

class Employee
{
int eno;
String enm;

Employee(int no,String nm)
{
eno=no;
enm=nm;
}

void empInfo()
{
System.out.println("Employee No : "+eno);
System.out.println("Employee Name : "+enm);
}
}

class Manager extends Employee
{
int month ,rate;

Manager(int no,String nm,int r,int m)
{
super(no,nm);
rate=r;
month=m;
}

void salaryInfo()
{
super.empInfo()
System.out.println("Salary is "+(rate*month));
}
}

class Test
{
public static void main(String args[])
{
Manager m1=new Manager(101,"Pravin",50000,1);
m1.salaryInfo();
}
}

Overloading :

An Overloading is process/ compile time polymorphism in which one class has many functions/methods with same name but different signatures.
Overloading concept is similar in c++and java even implementation .(except syntax)

Example in java :

class Overloading
{

void addition(int a,int b)
{
System.out.println("Addtion of two integers : "+(a+b));
}

void addition(double a,double b)
{
System.out.println("Addtion of two doubles : "+(a+b));
}
}

class Test
{
public static void main(String args[])
{
Overloading o1=new Overloading();
o1.addition(10,20);
o1.addition(35.50, 640.12);
}
}

Overriding :

An Overloading is process/ run time polymorphism in which many classes have one function/method with same name and with same signatures.
Overriding concept is similar in c++and java even implementation .(except syntax)

Example in Java :

abstract class A
{
void addition(int a,int b);
}

class B extens A
{
void addition(int a,b)
{
System.out.println("Addition is "+(a+b));
}
}

class Test
{
public static void main(String args[])
{
B b1=new B();
b1.addition(100,200);
}
}

3 (c)
Namespace in C++ & Package in Java :

Namespace in C++ :

-> A namespace is a containter for identifiers or declarative region that provides to a scope to the identifiers.

Simple Example of Namespace :

#include<iostream>
using namespace std;

namespace A
{
void demo()
{
cout<<"First method of the program!!";
}
}

namespace B
{
void demo()
{
cout<<"Second method of the program!!"
}
}

int main()
{
A::demo();
B::demo();
return 0;
}

Package in java :

A package is a container or a collection of classes,interfaces or sub directives.

Example :

package p1;

public class A
{
public void addition(int a,int b)
{
System.out.println("Addition of two numbers is "+(a+b));
}
}

package p2;
import p1.A;

class Test
{
public static void main(String args[])
{
A a1=new A();
a1.addition(100,200);
}
}
namepaces are nested while packages are flat.

3(d)
Inline methods:
A method with one or two line code for efficient or for fast execution that method is known as Inline method.

Example :

#include<iostream>

inline int addition(int a,int b)
{
return(a+b);
}

int main()
{
cout<<"Addition of two numbers is "<<addition(1,2);
return 0;
}

Accessor & Mutator :

Accessot and mutator are functions to set and get the values of the variables.

Example :

#include<iostream>
using namespace std;

class Demo
{
public:
int a;
void set(int a1) //accessor
{
a=a1;
}

int get() //mutator
{
return a;
}
};

int main()
{
Demo d1;
d1.set(100)

cout<<"Value of given variable is "<<d1.get();
return 0;
}