title: Java: calculating area of a triangle
body: <pre><code>import java.lang.Math;
  import java.awt.*
  public class Triangle implements Shape
  {
      java.awt.Point a;
      java.awt.Point b;
      java.awt.Point c;
  
      public Triangle(java.awt.Point a, java.awt.Point b, java.awt.Point c)
      {
          this.a = a;
          this.b = b;
          this.c = c;
      }    
  public double getArea( )
      {
         double area;
         return area = Math.abs((a-c)*(b-a)-(a-b)*(c-a));
      } ...
  </code></pre>
  
  <p><a href="http://upload.wikimedia.org/math/f/e/5/fe56529cdaaaa9bb2f71c1ad8a1a454f.png" rel="nofollow noreferrer">http://upload.wikimedia.org/math/f/e/5/fe56529cdaaaa9bb2f71c1ad8a1a454f.png</a> &lt;--area formula</p>
  
  <p>I am trying to calculate the area of a triangle from 3 points (x,y) from a 2D Cartesian coordinate system. I'm assuming that my above formula correctly yields the area of a triangle (if not, please correct me) but my compiler says "operator - cannot be applied to java.awt.Point,java.awt.Point". I'm assuming it's saying this because you cannot subtract points from each other, but each value in the formula is either an x or y value, not a point. How can I fix my code so this would work? 
  Thanks!</p>