Delving Further into Object-Oriented Concepts - Beginning Java Programming: The Object-Oriented Approach - page 245

class contain a getName() method. Therefore, the Master instance inherits the getName() method
directly from the Person class. Next, it will need to call the calculateGPA() method for John. The
Master class does not contain a calculateGPA() method, but the Graduate class, the superclass of
Master , does. Dynamic binding looks at the type of instance that John is: a Master and, therefore, a
Graduate . Therefore, the calculateGPA() method from the Graduate class is called.

For Anne, the same decision process occurs. There is no getName() method in any of the subclasses,
so the class hierarchy is considered to find that Anne is an Associate , which is an Undergraduate ,
which is a Student , which is a Person , and the getName() method from the Person class is called.
For her GPA, neither Associate nor Undergraduate has a calculcateGPA() method, so the
Student version of the method is called for Anne.

Sure enough, the console output shows two different GPAs, despite having the same grades, because
dynamic method invocation allows different versions of the method to be called depending on the
instance calling it.
John Adams: 0.865
Anne Philips: 0.792

the superclass object
As mentioned in the introduction to inheritance, all classes in Java descend from the class Object .
The Object class has several methods that are, therefore, inherited by every other class. You may
choose to use them directly or override them in your own classes.
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protected Object clone() : Creates and returns a copy of this object

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public boolean equals(Object obj) : Indicates whether some other object is “equal to”
this one

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protected void finalize() : Called by the garbage collector on an object when garbage
collection determines that there are no more references to the object

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public final Class getClass() : Returns the runtime class of an object

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public int hashCode() : Returns a hashcode value for the object

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public String toString() : Returns a string representation of the object

The clone() method can be used only if the class is Cloneable . If so, the default clone() method
creates a new object of the same class as the original object and with the same values for its instance
variables. If your original object references another object, the clone will reference the same object.
You may want to override the clone() method to create clones of both objects instead of sharing
the referenced object.

The equals() method was discussed in Chapter 5. It compares two objects for equality. To compare
two objects, this method uses the == operator, which gives the correct answer for primitive data
types. However, for objects, it returns true if the references are equal, meaning the two variables
point to exactly the same object. In most cases, you are more interested if the instance variables' val-
ues of both objects match. To accomplish this, you should override the equals() method according
to the needs of your class or program. For example, you might consider two Person objects equal
if their social security number is the same. Depending on the class, there might be different possible