Java - Should private instance variables be accessed in constructors through getters and setters method?

Question

I know that private instance variables are accessed through their public getters and setters method.

But when I generate constructors with the help of IDE, it initializes instance variables directly instead of initializing them through their setter methods.

Q1. So should I change the IDE generated code for constructors to initialize those instance variables through their setter methods.

Q2. If yes, then why IDE don't generate constructors code in that way?

============================= EDITED =======================================

• I use Eclipse and Netbeans IDE

• It's a general question. But as asked by @Lords would the answer depends on whether our constructor is public or protected or package private or private?

Answer 1

You should never call a non-final method from a constructor. A class constructor is used to initialize an object, and the object is not in a consistent state until the constructor returns. If your constructor calls a non-final method which is later overridden by a subclass, you can get strange, unexpected results because the object is not fully initialized when the overridden method is called.

Consider this contrived example:

class A {
    private int x;

    public A() {
        setX(2);
    }

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

    public int getX() {
        return x;
    }
}

class B extends A {
    private int number = 10;

    @Override        
    public void setX(int x) {
        // set x to the value of number: 10
        super.setX(number);
    }
}

public class Test {
    public static void main(String[] args) {
        B b = new B();
        // b.getX() should be 10, right?
        System.out.println("B.getX() = " + b.getX());
    }
}

The output of this program is:

B.getX() = 0

The reason is that B's number member is not initialized at the time setX is called, so its default value of 0 is used.

This article has a more thorough explanation, as does Effective Java.

Answer 2

Constructors are for initialization. Initialize private instance variables directly in the constructor. Methods define an object's behavior. Behavior occurs after instantiation/initialization. Manipulate the state of your instance variables with your setter methods. That's classic OOP thinking and probably why your IDE is generating the code it does.

Answer 3

That depends. If your setters/getters are simply accessing the members you should access them directly. If you also have some code along with it, use setters.