Скачать или смотреть Java - Day 71 (in Telugu) - difference between dynamic binding and static binding

/*
difference between static binding and dynamic binding
*/

import java.util.*;

interface Shape{
void input();
void area();
void sides();
}
class Rect implements Shape{
int len,bre;
public void input(){ Scanner sc1 = new Scanner(System.in); System.out.print("enter Rect length:"); len=sc1.nextInt(); System.out.print("enter Rect breadth:");bre=sc1.nextInt();}
public void area(){ System.out.println("Rect area:"+(len*bre)); }
public void sides(){ System.out.println("\nRect sides: 4"); }
}
class Triangle implements Shape{
int base,ht;
public void input(){ Scanner sc2 = new Scanner(System.in); System.out.print("enter triangle base:"); base=sc2.nextInt(); System.out.print("enter triangle height:");ht=sc2.nextInt();}
public void area(){ System.out.println("Triangle area:"+(base*ht/2)); }
public void sides(){ System.out.println("\nTriangle sides: 3"); }
}
class Circle implements Shape{
int rad;
public void input(){ Scanner sc4 = new Scanner(System.in); System.out.print("enter Circle radius:"); rad=sc4.nextInt(); }
public void area(){ System.out.println("Circle area:"+((22/7.0)*(rad*rad))); }
public void sides(){ System.out.println("\nCircle sides: 0"); }
}
public class DynamicBind{
public static void main(String arg[]){
Scanner sc3 = new Scanner(System.in);
System.out.println("1.Rect");
System.out.println("2.Triangle");
System.out.println("3.Circle");
System.out.print("Choose the shape (1/2/3):");
int type = sc3.nextInt();
Shape s = null;

if(type==1)
s = new Rect();
else if(type==2)
s = new Triangle();
else if(type==3)
s = new Circle();
else{
System.out.println("\ninvalid option");
System.exit(0);
}

s.input(); // dynamic binding
s.sides(); // dynamic binding: taking decision at runtime about linking/binding/relating between "method call" & "method definition"
s.area(); // dynamic binding
}
}
/*
dynamic binding is possible only when parent child relation exists.
dynamic binding is possible only when overrding involves.

solution1:
if(type==1)
s = new Rect();
else if(type==2)
s = new Triangle();
else // removed if
s = new Circle();

s.input();
s.sides();
s.area();

solution2:
if(type==1)
s = new Rect();
else if(type==2)
s = new Triangle();
else if(type==3)
s = new Circle();

if(s!=null){
s.input();
s.sides();
s.area();
}

solution3:
if(type==1)
s = new Rect();
else if(type==2)
s = new Triangle();
else if(type==3)
s = new Circle();
else
return;

s.input();
s.sides();
s.area();

solution4:
throw an exception and handle it properly.

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-------------
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if-else, while/for, switch, arguments, array, function/method)
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-------------
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--------------------
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*/