package Week2.inheritance;
/*
* Inheritance :: Inheritance of Instance Variables
*
* A subclass object inherits all instance variables from the superclass
declaration.
*
* What the accessibility modifiers public, protected, and private specify
regarding
* attributes declared in a superclass, is whether or not those attributes are
* directly accessible in a subclass. In particular, the rules are:
*
* 1. public attributes are directly accessible in subclass objects. In fact,
* public attributes of objects are directly accessible from the methods of
* objects of any class—which is why we never declare public attributes.
*
* 2. protected attributes are directly accessible in subclass objects,
* but they are not directly accessible from within the methods of objects
* of other classes.
*
* 3. private attributes are only accessible in objects of the superclass;
* they are not directly accessible from within the methods of subclass objects.
*
* Consequently, within the sub object mPublic and mProtected are directly
* accessible, but mPrivate is not. Example:
*
* public class Sub extends Super {
* public Sub() {
* mPublic = 0; // Legal because mPublic is public.
* mProtected = 0; // Legal because mProtected is protected.
* mPrivate = 0; // Illegal because mPrivate is private.
* }
*}
*
* The last case is why I used to get confused about private instance variables
* being inherited. They are inherited, but they are not directly accessible. So
* how do we access a private inherited instance variables?
* */
/*
* Accessing Private Instance Variables in a Subclass
public class ImplementingInheritance {
/*
* To specify that a subclass Sub inherits from a superclass Super we write:
* public class Sub extends Super { ... } Sub inherits all instance variables
—whether
* public, protected, or private—from Super. For example:
* public class Super {
* // mPublic is public for illustration purposes. Do not ever declare
a public
* // instance variable.
* public int mPublic;
* protected int mProtected;
* private int mPrivate; ...
* }
* public class Sub extends Super {
* // mPublic is inherited from Super.
* // mProtected is inherited from Super.
* // mPrivate is inherited from Super. ...
* }
* */
}
*
* How do we access a private inherited instance variables? Through superclass-
declared
* accessor and mutator methods. Example:
*
* public class Super {
* // mPublic is public for illustration purposes. Do not ever declare a public
* // instance variable.
* public int mPublic;
* protected int mProtected;
* private int mPrivate;
* ...
* public int getPrivate() { return mPrivate; }
* public void setPrivate(int pNewPrivate) { mPrivate = pNewPrivate; }
* }
* public class Sub extends Super {
* public Sub() {
* mPublic = 0; // Legal because mPublic is public.
* mProtected = 0; // Legal because mProtected is protected.
* setPrivate(0); // Legal because setPrivate() is public.
* int x = getPrivate(); // Legal because getPrivate() is public. }
* }
*}
* */
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