I do not find formula for determination of area of Quadrilateral with four vertices (points). Who is strong in math and can help with Java formula for it. Thanks very much. I know only that 'convex quadrilaterals are divided into two triangles by any of their diagonals'.

CodePudding user response：

Having vertices coordinates we can calculate are of any polygon using shoelace formula

Java code from here

public static double polygonArea(double X[], double Y[], int n)
{
    // Initialize area
    double area = 0.0;
 
    // Calculate value of shoelace formula
    int j = n - 1;
    for (int i = 0; i < n; i  )
    {
        area  = (X[j]   X[i]) * (Y[j] - Y[i]);
         
        // j is previous vertex to i
        j = i;
    }
 
    // Return absolute value
    return Math.abs(area / 2.0);
}

For specific case of quadrilateral we can write result without loops

Area = 0.5 * ((x[0]*y[1] x[1]*y[2] x[2]*y[3] x[3]*y[0]) - 
              (x[1]*y[0] x[2]*y[1] x[3]*y[2] x[0]*y[3]))