Menu Driven Program to find area of a Triangle as per the user's choice.

import java.util.*;

public class Triangle

{

public static void main(String args[])

{

Scanner in=new Scanner(System.in);

double area=0.0D,s,b,a,m,n,p;

int choice;

System.out.println("Enter your Choice : 1 for Equilateral Triangle, 2 for Isosceles Triangle and 3 for Scalene Triangle");

choice=in.nextInt();

switch(choice)

{

case 1: System.out.println("Enter the side of the Equilateral Triangle");

s=in.nextDouble();

area=(Math.sqrt(3)/4)*s*s;

break;

case 2: System.out.println("Enter the side and base of the Isosceles Triangle");

a=in.nextDouble();

b=in.nextDouble();

area=(1.0/4.0)*b*Math.sqrt(4*a*a-b*b);

break;

case 3:System.out.println("Enter the sides of the scalene Triangle");

m=in.nextDouble();

n=in.nextDouble();

p=in.nextDouble();

s=(m+n+p)/2.0;

area=Math.sqrt(s*(s-m)*(s-n)*(s-p));

break;

default:System.out.println("Wrong Choice");

}

System.out.println("Area= "+area);

}

}