在Java Constructor中访问变量并在其余的类中使用

Question

So this is a rather simple question I'm sure for java and been answered before, I just can't seem to exactly find this answer. Prefer if someone could just comment the answer.

If you have

class Triangle{
private double x1,x2,x3,y1,y2,y3;
public Triangle(Point point1, Point point2, Point point3) 
{ 
x1=point1.getX();
y1=point1.getY();
x2=point2.getX();
y2=point2.getY();
x3=point3.getX();
y3=point3.getY();

//Trying to get x and y values of point1-point3

}

double width=x1-x2;
double length=y3-y2;

public double area() 
{ 
return (length * width)/2; 
} 

So basically I have points defined to take two variables x and y and I'm trying to calculate this area of a triangle. So someone gives 3 points to make this triangle and I'm trying to get those values from the points and I do have getters for my points but I'm just ending up with nothing for length and width.

Answer 1

If you want code outside of A to be able to access newid , then you need to add getter and/or setter methods to A .

For example:

public class A {

    private int newid;

    public A(int id){
        this.newid = id;
    }

    public int getNewid() {
        return this.newid;
    }

    public void setNewid(int id) {
        this.newid = id;
    }
}

Note that the this. qualification is not necessary in this particular example.

On the other hand, if you want to access newId within the class A , then ...

public class A {
    private int newid;

    ...

    public double b() {
       weight = newid * 5;
       // or 
       weight = this.newid * 5;
       ...
    }
}