Java Access Modifier Best Practice

Question

This may seem a basic question, but I'd like to get this right.

I have a Class 'AWorld'. Within that class, I have a method that draws a border, depending on the map size set by the user.

If the variable 'mapSize' is private, but I want to access it's value from within the same class, is it more appropriate to reference it directly, or use a getter method.

The code below should explain what I'm wanting to know.

package javaFX;

public class AWorld {
    //initialized later
    AWorld newWorld;

    private int mapSize = 20;

    public int getMapSize()
    {
        return mapSize;
    }

    public void someMethod()
    {
        int var = newWorld.mapSize; //Do I reference 'mapSize' using this...
    }
    // Or...

    public void someOtherMethod()
    {
        int var = newWorld.getMapSize(); //Or this?
    }
    public static void main(String[] args) {}

}

Answer 1

Either of those is ok since you're getting a primitive field. If the get method does another operation before returning the data e.g. performing a math operation on the value, then it would be better to use it rather than calling the field directly. This is specially meant when using proxy/decorator pattern on your classes.

Here's an example of the second statement from above:

//base class to be decorated
abstract class Foo {
    private int x;
    protected Foo foo;
    public int getX() { return this.x; }
    public void setX(int x) { this.x = x; }
    public Foo getFoo() { return this.foo; }

    //method to prove the difference between using getter and simple value
    public final void printInternalX() {
        if (foo != null) {
            System.out.println(foo.x);
            System.out.println(foo.getX());
        }
    }
}

//specific class implementation to be decorated
class Bar extends Foo {
    @Override
    public int getX() {
        return super.getX() * 10;
    }
}

//decorator
class Baz extends Foo {
    public Baz(Foo foo) {
        this.foo = foo;
    }
}

public class Main {
    public static void main(String[] args) {
        Foo foo1 = new Bar();
        foo1.setX(10);
        Foo foo2 = new Bar(foo1);
        //here you see the difference
        foo2.printInternalX();
    }
}

Output:

10
100