JAVA
Constructor
and Inheritance
Fill
in the blanks
1. Constructor
means Creating an object
2. Destructor
means Deleting an object
3.Class name
should be same as method name is called Constructor
4.Constructor
should not have any return value/type.[T/F]. True
5.Constructor
can’t be Overloaded.[T/F]. False
6.Constructor
without argument is called Default Constructor
7.Constructor
with argument is called Parameterized Constructor
8.Constructor
with the argument will be an object is called Copy Constructor
9.This
keyword used to refer the current object.
10.Write
access specifiers public, private
, protected and default
11.Write a keyword for inheritance extends
Answer
the Following Questions
(4
marks)
1.Write a program for default and
parameterized Constructor
class Person{
String name;
int age;
Person()
{
name="Unknown";
age=0;
}
Person(String n, int a){
name=n;
age=a;
}
void show(){
System.out.println("Name:
"+name+" , Age: "+age);
}
public static void main(String args[]){
Person p;
p=new Person();
p.show();
p=new
Person("Babu",35);
p.show();
}
}
2.Write a program for Static Method
class Recta{
int length;
int breadth;
static int count;
Recta() {
count++;
}
static {
count=0;
System.out.println("Inside
static block");
}
static void
displayCount()
{
System.out.println("No
of Object"+count);
}
public static void
main(String args[])
{
Recta
r1, r2;
Recta.displayCount();
r1=new
Recta();
r1.displayCount();
r2=new
Recta();
Recta.displayCount();
}
}
3.Write a program for Single Inheritance
File
name: A.java
class
A{
int
i, j;
void
showij(){
System.out.println("i
and j:"+i+" "+j);
}
}
//
Create a subclass by extending class A.
File
name: B.java
class
B extends A{
int
k;
void
showk() {
System.out.println("k
: "+k);
}
void
sum() {
System.out.println("i+j+k: "+(i+j+k));
}
}
File
name: SimpleInheritance.java
class
SimpleInheritance{
public
static void main(String args[]){
A
superOb=new A();
B
subOb=new B();
//The
superclass may be used by itself.
superOb.i=10;
superOb.j=20;
System.out.println("Contents
of superOb:");
superOb.showij();
System.out.println();
/*The
subclass has access to all public members fits
superclass.*/
subOb.i=7;
subOb.j=8;
subOb.k=9;
System.out.println("Contents
of subOb:");
subOb.showij();
subOb.showk();
System.out.println();
System.out.println("Sum
of i , j and k in subOb:");
subOb.sum();
}
}
Answer
the Following Questions
(10
marks)
1.Write a program for Constructor
Overloading
File name: Cons.java
class Cons{
double
width,height,depth;
Cons(double
w,double h,double d){
width=w;
height=h;
depth=d;
}
//constructor used when
no when no dimensions specified
Cons() {
width=-1; //use-1 to indicate
height=-1; //an uninitialized
depth=-1; //box
}
//contructor used
when cube is created
Cons(double len) {
//this can be
used to call different constructor from same class.
this(len,len,len);
}
void volume()
{
System.out.println("volume:"+width*height*depth);
}
}
File name: ConsOverload.java
class ConsOverload {
public static void
main(String args[]) {
Cons
mybox1=new Cons(10,20,15);
Cons
mybox2=new Cons();
Cons
mycube=new Cons(7);
mybox1.volume();
mybox2.volume();
mycube.volume();
}
}
2.Write a program for Method Overriding
File
name: Figure.java
class
Figure{
double
dim1;
double
dim2;
Figure(double
a, double b) {
dim1
=a;
dim2
=b;
}
double
area() {
System.out.println("Area
for Figure is undefined.");
return
0;
}
}
File
name: Rectangle.java
class
Rectangle extends Figure {
Rectangle(double
a,double b) {
super(a,b);
}
//
override area for rectangle
double
area() {
System.out.println("Inside
Area for Rectangle.");
return
dim1* dim2;
}
}
File
name: Triangle.java
class
Triangle extends Figure {
Triangle(double
a, double b) {
super(a,
b);
}
//override
area for right triangle
double
area() {
System.out.println("Inside
Area for Triangle.");
return
dim1 * dim2/ 2;
}
}
File
name: FindAreas.java
class
FindAreas{
public
static void main(String args[]) {
Figure
f =new Figure(10, 10);
Rectangle
r =new Rectangle(9,5);
Triangle
t = new Triangle(10, 8);
Figure
figref;
figref
= r;
System.out.println("Area
is" + figref.area());
figref
= t;
System.out.println("Area
is" + figref.area());
figref
= f;
System.out.println("Area
is" + figref.area());
}
}
3.Write a program for Single Inheritance
using Super keyword.
File
name: Book.java
import
java.lang.*;
import
java.io.*;
class
Book
{
int
bno;
String
bname;
double
price;
public
Book(int n,String bn,double p)
{
bno=n;
bname=bn;
price=p;
}
void
display()
{
System.out.println("\nBook
Number = " + bno);
System.out.println("\nBook
Number = " + bname);
System.out.println("\nBook
Number = " + price);
}
}
File
name: Purchase.java
class
Purchase extends Book
{
int
qord;
double
netcost;
public
Purchase(int n1,String bn1, double p1,int q)
{
super(n1,bn1,p1);
//Base Class Constructor
qord=q;
}
void
display() //Overriding of methods
{
netcost=qord*super.price; //Baseclass Variable
super.display(); //Base
class Function
System.out.println("\nQuantity
ordered = "+qord);
System.out.println("\nNet
cost="+netcost);
}
}
File
name: Inherit1.java
class
Inherit1
{
public
static void main(String args[])
{
Purchase
pur =new Purchase(10,"Black book of java",500.00,34);
pur.display();
}
}
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