Error with constructor

Question

MyCircle c = new MyCircle(2,5,8);/// Instanciei um objeto no main.

---

public class MyCircle {

    private MyPoint center; 
    private int radius=1;

    public MyCircle(int x,int y,int radius) {

       this.center.getX(x); ///na classe MyPoint ha a variável x e y com os respectivos gets e sets
       this.center.setY(y);
       this.radius = radius;

    }

    Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: questao.MyPoint.getX
    at questao.MyCircle.<init>(MyCircle.java:17)
    at questao.Questao.main(Questao.java:27)
C:\Users\M\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
FALHA NA CONSTRUÇÃO (tempo total: 0 segundos)

Answer 1

This is a compile problem. There is no method getX who receives a int as a parameter in the class MyPoint.

However, this makes sense, because getters have no parameters. The idea of this code seems to be to define which is the center and not to discover which is. In other words, you should call the Setter (setX), and not the getter (getX). Notice that with the Y, you do it right and call the getter (getY). I mean, what you wanted was this:

public class MyCircle {
    private MyPoint center; 
    private int radius;

    public MyCircle(int x, int y, int radius) {
       this.center.setX(x);
       this.center.setY(y);
       this.radius = radius;
    }
}

But even if you fix this problem, you’ll still get one NullPointerException because you can’t call the Setter of the object center when there is no object yet center. The solution is this:

public class MyCircle {
    private MyPoint center; 
    private int radius;

    public MyCircle(int x, int y, int radius) {
       this.center = new MyPoint();
       this.center.setX(x);
       this.center.setY(y);
       this.radius = radius;
    }
}

public class MyPoint {
    private int x;
    private int y;

    public MyPoint() {
    }

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }
}

However, there is still one more question to consider. Note that the MyCircle is constructed by means of constructor parameters while the constructor MyPoint is built by means of setters. The constructor’s parameter-based approach often produces code that is easier to move, easier to understand, simpler, smaller, and less likely to produce unpleasant surprises. So let’s change the approach of MyPoint to use the constructor’s parameter-based approach:

public class MyCircle {
    private MyPoint center; 
    private int radius;

    public MyCircle(int x, int y, int radius) {
       this.center = new MyPoint(x, y);
       this.radius = radius;
    }
}

public class MyPoint {
    private int x;
    private int y;

    public MyPoint(int x, int y) {
        this.x = x;
        this.y = y;
    }
}