Java：getSlope 无法解析为变量

Question

I am having trouble with printing getSlope() to the console, with any values I plug in for (x1 - x2) / (y1 - y2), Java ends up dividing by zero every time I run the program.

Slope class:

public class Slope {
    private int x1;
    private int x2;
    private int y1;
    private int y2;

    public Slope(int a, int b, int c, int d) {
        a = x1;
        b = x2;
        c = y1;
        d = x2;
    }

    public void setSlope(int a, int b, int c, int d) {
        x1 = a;
        x2 = b;
        y1 = c;
        y2 = d;
    }

    public int getX() {
        return (x1 - x2);
    }

    public int getY() {
        return (y1 - y2);
    }

    public void sayThis() {
        System.out.println(getX()/getY());
    }
}

testSlope Class:

public class testSlope {

    public static void main(String[] args) {
        Slope slope = new Slope(10, 5, 1, 2);
        slope.sayThis(); 
    }
    //Exception in thread "main" java.lang.ArithmeticException: / by zero
    //    at Slope.getSlope(Slope.java:22)
    //    at Slope.sayThis(Slope.java:26)
    //    at testSlope.main(testSlope.java:5)

}

Answer 1

The problem is that your constructor is wrong. It should be like this:

public Slope(int a, int b, int c, int d) {
    x1 = a;
    x2 = b;
    y1 = c;
    y2 = d;
}

Answer 2

public class Slope {

private int x1;
private int x2;
private int y1;
private int y2;

public Slope(int a, int b, int c, int d) {

    y2 = d;
    y1 = c;
    x2 = b;
    x1 = a;

    System.out.println(x1 - x2 / y1 - y2);
}

public static void main(String[] args) {
    Slope slope = new Slope(70, 80, 1, 2);
}

}