Ch 3 Java Inheritance

subclass

-The class which inherits the properties of other -(derived class, child class)

superclass

-the class whose properties are inherited -(base class, parent class)

Class

A blueprint for an object.

Class Hierarchy

A child of one class can be the parent of another, creating a...

one, many

A class can have exactly ___ parent class, but it might have ____ child classes.

subclass

A class derived from a superclass. Also called a child class.

superclass

A class from which another is derived. Also called a parent class or base class.

What does the protected access class modifier do?

Allows subclasses to have access to superclass data member and methods marked as such.

Why should you never use == to compare the attributes of objects?

Because it compares whether or not two references point to the same object in memory, not if they're attributes are the same. equals() can be overridden. == cannot.

@Override is used to ________?

Declare that a superclass method is being overriden. It is optional, and placed directly above the method that is doing the overriding. It is also a safety mechanism and will return an error if no superclass method exists in the same format as the overridden method.

Inheritance uses a ______ relationship.

IS-A

A(n) ______ cannot be instantiated

Interface

What does the "super" reference do?

It can be used to refer to superclass methods, and is used to refer to the superclass constructor.

toString() can be overridden at multiple _______ to meet class implementations and outputs.

Levels

Why do we use inheritance?

Minimizes redundant code for common traits

All classes are subclasses of the _________ class.

Object

If no direct superclass is specified, than a class will inherit from the __________ class by default.

Object

In Java, all classes inherit from the ______ class by default

Object

Software Reuse

One purpose of inheritance.

superclass and base class

Other names for the parent of a subclass are ______ and ______ .

child, derived

Other names for the sub-class of a parent are ___ class and ___ class.

Subclasses can _________ methods defined in a superclass.

Override

______ is when a subclass redefines a method of it's parent class

Overriding

________ members are inherited by the child class, but cannot be referenced directly by name. may be used indirectly by calling methods.

Private.

Class Hierarchy

The "family tree" of classes.

What is inheritance?

The action of taking methods and fields from a parent class and allowing a child or subclass to inherit and use those methods and fields

subclass

The class which inherits the properties of other It is also called a derived class or child class

superclass

The class whose properties are inherited It is also called a base class or parent class

A private member of a class is visible only to ______

The defining class

is-a

The relationship between a child and parent class.

What is the difference between a superclass and a subclass?

The superclass is a generalized class containing all common methods and fields The subclass is the child class that adds methods and fields that are unique to it.

How do you use inheritance in a class?

Use the extends keyword after the class name: public class Car extends Vehicle

Overrides

When a child class defines a method with the same name/signature as a method of the parent class, the child class... the parent.

The Principle of Encapsulation

When variables of the parent class are declared public so that the child class can access them, the ... is violated.

concrete class

a class for which you can create an object (basically anything that isn't abstract)

abstract class

a class for which you cannot create an object

Subclasses

a class that is a special case of an existing class

An ______ cannot be instantiated

abstract class

class for which you cannot create obects

abstract class

public & private are examples of...

access modifiers

cannot

an abstract class ___ be instantiated

instantiated

an interface cannot be

The subclass inherits these from the superclass

behavior and state

An abstract method does not have a ______

body

A class ______ extend multiple classes

cannot

extends syntax

class Super { ..... ..... } class Sub extends Super { ..... ..... }

a class which you can create objects for

concrete class

Object

every class in Java is a descendent of the ___ class

A public member of a class is visible to ______

everything

In Java, a class can ______ up to one other class to inherit from it

extend

Classes use ______in the header to create child classes.

extends

The keyword used to inherit a class is...

extends

Inheritance is a mechanism in which one class can inherit the ______ and methods of another "parent" class

fields

a class can implement one or more interfaces

helped Java get rid of the impossibility of multiple inheritance.

If no superclass constructor reference exists in the subclass constructor, then the superclass _________________ a default superclass constructor _________ before any code is run in the constructor.

implicitly calls; super()

IS-A Relationship

is a way of saying: This object is a type of that object

extends

is the keyword used to inherit the properties of a class

An Interface consists solely of ______

method signatures

Inheritance is a mechanism in which one class can inherit the fields and ______ of another "parent" class

methods

A class derived from an abstract parent must _______ all of it's parent's abstract methods.

override , or the derived class will also be considered abstract.

all methods of classes in the same package can access the feature

package access

the default access when no access modifier is given

package access

Inheritance is a mechanism in which one class can inherit the fields and methods of another "______" class

parent

four levels of controlling access to fields

public access, private access, protected access, package access

single inheritance B -> A

public class A { ..... } public class B extends A { ..... }

overriding

redefining a method in a subclass when we want a method in the child class to behave differently than in its parent class

more specialized class that inherits from the superclass

subclass

Any new instance fields that you define in the subclass are present only in

subclass objects

A protected member of a class is visible to ______

subclasses

To call the constructor of a parent class, you must use the ______ keyword

super

use this keyword to call a method of the superclass

super ex. super.deposit(amount);

How do you call upon the constructor of a superclass?

super();

Invoking the parameterized Superclass Constructor

super(values);

first

the call using super must be the ____ statement in the constructor

If you define a method that does not exist in the superclass then,

the new method can only be applied to subclass objects

Inheritance

the process where one class acquires the properties (methods and fields) of another. -manageable in a hierarchical order.

interface

you can have reference variables with ___ types

salespeople

you have an employee class and you want to have a special class for employees who are ______.