This is how you calculate the area of a triangle, hope you guys find this useful.

```
import java.text.DecimalFormat;
import java.util.Scanner;
public class Exercise2_15 {
// find the area of a triangle
public static void main (String [] args) {
double side1 = 0;
double side2 = 0;
double side3 = 0;
Scanner input = new Scanner(System.in);
//obtain three points for a triangle
System.out.print("Enter three points for a triangle: ");
double side1x = input.nextDouble();
double side1y = input.nextDouble();
double side2x = input.nextDouble();
double side2y = input.nextDouble();
double side3x = input.nextDouble();
double side3y = input.nextDouble();
//find length of sides of triangle
side1 = Math.sqrt(Math.pow((side2x - side1x), 2)+ Math.pow((side2y - side1y), 2));
side2 = Math.sqrt(Math.pow((side3x - side2x), 2)+ Math.pow((side3y - side2y), 2));
side3 = Math.sqrt(Math.pow((side1x - side3x), 2)+ Math.pow((side1y - side3y), 2));
double s = (side1 + side2 + side3) / 2;
double area = Math.sqrt(s * (s - side1) * (s - side2) * (s-side3));
DecimalFormat myFormatter = new DecimalFormat("#,##0.00");
System.out.println("The area of the triangle is " + myFormatter.format(area));
}
}
```