import java.util.Scanner;
import java.io.File;

public class EquationTest{
    public static void main(String[] args){
        File file = new File ("slope.txt");
        try{
            Scanner reader = new Scanner(file);
            int x1 = 0;
            int x2 = 0;
            int y1 = 0;
            int y2 = 0;
            while(reader.hasNext()){
                for(int x = 0; x <=3; x++){
                    int num = reader.nextInt();
                    if (x == 0)
                        x1 = num;
                    else if (x == 1)
                        y1 = num;
                    else if (x == 2)
                        x2 = num;
                    else
                        y2 = num;
                }
                Line line = new Line(x1, x2, y1, y2);

                System.out.println(line);
            }
        }
        catch (Exception e){

        }
    }
}

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public class Line{
    double x1, x2, y1, y2;

    public Line(int x1, int x2, int y1, int y2){
        this.x1 = x1;
        this.x2 = x2;
        this.y1 = y1;
        this.y2 = y2;
    }

    public boolean hasSlope(){
        if (x1 == x2)
            return false;
        else
            return true;
    }

    public double getSlope(){
        if (hasSlope())
            return ((this.y2 - this.y1) / (this.x2 - this.x1));
        else
            return 0;
    }

    public String toString(){
        String points = "points (" + x1 + ", "+ y1 + ") and (" + x2 + ", " + y2 + ") \n";
        String theLine;
        if(hasSlope()){
            String slope = "slope: " + getSlope() + "\n";
            String equation = "equation: y = " + getSlope() + " * x + " + (y1 - (getSlope() * x1)) + "\n";

            theLine =  points +  slope + equation;
        }
        else{
            String undefined = "slope is undefined";
            theLine = points + undefined;
        }
        return theLine;
    }
}

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78 86 92 91
66 60 72 72
77 73 73 85
82 88 81 77