Logic error in program which uses trapezoidal approximation to find the area under curve

Question

Can anyone find why this is this class wont run? I've made some error or another, but I can't seem to see the error. I instantiate an object and print what should be its area using what I believe is the proper notation to return the value I desire. The information in the object should evaluate to ~7.2.

public class TrapApx
{
    private double x1;
    private double x2;
    private double distance;
    private double numberOfSections;
    private double changeInX;
    private double area = 0;

    public TrapApx(double firstX, double secondX, double numOfSec)
    {
        x1 = firstX;
        x2 = secondX;
        numberOfSections = numOfSec;
    }

    public double distance()
    {
        return distance = x2 - x1;
    }

    public double changeX()
    {
        return changeInX = distance / numberOfSections;
    }

    public double funcX(double x)
    {
        return Math.sqrt(x-1);
    }

    public double areaApx()
    {
        for(double x = x1; x < x2; x += changeInX)
        {
            area += (funcX(x) + funcX(x + changeInX))/2 * changeInX;
        }
        return area;
    }
}

public class TrapApxTest
{
    public static void main(String []args)
    {
        TrapApx one = new TrapApx(1, 6, 5);
        System.out.println(one.areaApx());
    }
}

and I tried to see if something was not functioning with one of my variables or their mutations, so I created this static class with no objects and tested it procedurally, and it returned the proper answer.

public class tester
{
    public static double funcX(double x)
    {
        return Math.sqrt(x-1);
    }

    public static void main(String []args)
    {
        double x1 = 1,
               x2 = 6,
               distance = x2 - x1,
               numberOfSections = 5,
               changeInX = distance / numberOfSections,
               area = 0;

        for(double x = x1; x < x2; x += changeInX)
        {
            area += (funcX(x) + funcX(x + changeInX))/2 * changeInX;
        }

        System.out.println(area);
    }
}

Thanks for the help, guys.

Answer 1

The problem is that you never run the distance() method, so the distance field stays at zero. It's a really terrible idea to give a field and a method the same name.