I'm doing this project where I need to have this specific class structure and find the slope. I need to somehow find the slope using points 1 and 2 (p1, p2).

//file MyPoint

import java.text.DecimalFormat;

public class MyPoint {

    private double x;
    private double y;

    public MyPoint() {
        double xP = x;
        double yP = y;
    }

    public double getX(double x) {
        return x;
    }

    public double getY(double y) {
        return y;
    }

    public String toString() {
        DecimalFormat df_obj = new DecimalFormat("#.###");
        return "("   df_obj.format(getX(x))   ","   df_obj.format(getY(y))   ")";
    }

}



//file MyLine

public class MyLine {

    private MyPoint p1;
    private MyPoint p2;
    private double slope;
    private double xint;
    private double yint;

    public MyLine(MyPoint p1, MyPoint p2) {
        p1 = new MyPoint();
        p2 = new MyPoint();
    }

    public static MyPoint getPointOne(MyPoint p1) {
        return p1;
    }

    public static MyPoint getPointTwo(MyPoint p2) {
        return p2;
    }

    public static double getSlope() {
        double slope = //don't know what to put here in order to get the slope from p1 and p2;
        return slope;
    }

}

CodePudding user response：

The slope is calculated as rise/run which means delta Y divided by delta X.

double slope = (p1.getY() - p2.getY())/(p1.getX() - p2.getX());

and the equation of the line is y = slope*x b where b is the y-intercept (where the line crosses the y-axis if extended that far).

double b = y - slope*x;  // use either point for x,y

CodePudding user response：

A common slope calculation between 2 points would be:

    slope = DeltaX / DeltaY = (x2 - x1) / (y2 - y1)

So in your getSlope() method you'd use:

    double slope = (p2.getX() - p1.getX()) / (p2.getY() - p1.getY());

By the way I think there are a couple of mistakes in your code:

1. your getX() and getY() don't need to have 'x' and 'y' respectively as parameters. The x and y values are inside the MyPoint class' p1 and p2 instances.
2. On the other hand, the MyPoint constructor needs to receive the 'x' and 'y' parameters, in order to assign them to the inner xP and yP variables respectively.