Inheritance - Java Software Solutions: Foundations of Program Design - page 480

Summary of Key Concepts

Inheritance is the process of deriving a new class from an existing one.

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One purpose of inheritance is to reuse existing software.

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Inheritance creates an is-a relationship between the parent and child
classes.

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Protected visibility provides the best possible encapsulation that permits
inheritance.

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A parent's constructor can be invoked using the super reference. ■

A child class can override (redefine) the parent's definition of an inherited
method.

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The child of one class can be the parent of one or more other classes, cre-
ating a class hierarchy.

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Common features should be located as high in a class hierarchy as is rea-
sonably possible.

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All Java classes are derived, directly or indirectly, from the Object class.

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The toString and equals methods are inherited by every class in every
Java program.

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An abstract class cannot be instantiated. It represents a concept on which
other classes can build their definitions.

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A class derived from an abstract parent must override all of its parent's
abstract methods, or the derived class will also be considered abstract.

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Inheritance can be applied to interfaces so that one interface can be
derived from another.

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Private members are inherited by the child class, but cannot be referenced
directly by name. They may be used indirectly, however.

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Software design must carefully and specifically address inheritance. ■

The final modifier can be used to restrict inheritance.

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The classes that represent Java GUI components are organized into a class
hierarchy.

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A listener class can be created by deriving it from an event adapter class. ■

A Timer object generates action events at regular intervals and can be used
to control an animation.

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