4. Java OOP. 5. Abstract Classes

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4. Java OOP. 5. Abstract Classes

Содержание

2. Abstract Classes An abstract class is a class that is declared abstract Abstract classes cannot be
3. Abstract Methods An abstract method is a method that is declared without an implementation: abstract void
4. An Abstract Classes II A subclass of an abstract class usually provides implementations for all of
5. Example: Abstract DepoBase Class Modify 442InterestSum project using DepoBase as an abstract class. * Infopulse Training
6. Example: Abstract DepoBase Class See 451AbstractDepo project for the full text * Infopulse Training Center
7. How to Create and Use Library To create depo library: Right click on the app package
8. Interfaces An interface is a reference type, similar to a class, that can contain only constants,
9. Defining an Interface An interface declaration consists of: modifiers the keyword interface the interface name a
10. Interface Definition Example public interface GroupedInterface extends Interface1, Interface2, Interface3 { // constant declarations double E
11. The Interface Body The interface body contains method declarations for all the methods included in the
12. Use an Interface To use an interface, you write a class that implements the interface When
13. Interfaces and Multiple Inheritance In Java, a class can inherit from only one class but it
14. Using an Interface as a Type You can use interface names anywhere you can use any
15. Exercise: InterestInterface Modify 442InterestSum project using interface * Infopulse Training Center
16. Exercise: InterestInterface See 452InterfaceDepo project for the full text * Infopulse Training Center
17. Cloning (1 of 2) Use clone() method to get independent object instead of object’s assignment clone()
18. Cloning (2 of 2) The clone method is a protected method of Object, which means that
19. Deep Cloning To make a deep copy, you have clone the mutable instance fields in the
20. Example: DepoBase Cloning public abstract class DepoBase implements Cloneable{ . . . . . . public
21. Interfaces in Java SE 8 The interface body can contain: abstract methods (followed by a semicolon,
22. Interface Default Methods You specify that a method definition in an interface is a default method
23. Exercise: Default Method Modify 452InterfaceDepo project: Remove abstract DepoBase class Add calculateInterest method as default method
24. Exercise: Default Method See 453DefaultMethod project for the full text
25. Functional Interfaces A functional interface is any interface that contains only one abstract method A functional
26. Lambda Expression A lambda expression looks a lot like a method declaration You can consider lambda
27. Example of Lambda Expression I public class Calculator { interface IntegerMath { int operation(int a, int
28. Example of Lambda Expression II public static void main(String... args) { Calculator myApp = new Calculator();
29. Example of Lambda Expression See 454LambdaCalulator for the full text
30. Lambda Expression Syntax I A lambda expression consists of the following: a comma-separated list of formal
31. Lambda Expression Syntax II You can omit the data type of the parameters in a lambda
33. Скачать презентацию

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Abstract Classes
An abstract class is a class that is declared abstract
Abstract

classes cannot be instantiated, but they can be subclassed

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Abstract Methods
An abstract method is a method that is declared

without an implementation:
abstract void moveTo(double deltaX, double deltaY);
If a class includes abstract methods, the class itself must be declared abstract

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An Abstract Classes II
A subclass of an abstract class usually provides

implementations for all of the abstract methods in its parent class
If it does not, the subclass must also be declared abstract
Abstract classes can contain fields and implemented methods (partial implementation)
An abstract class may have static fields and static methods. You can use these static members with a class reference as you would with any other class

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Example: Abstract DepoBase Class
Modify 442InterestSum project using DepoBase as an abstract

class.

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Sum = 1763.41

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Example: Abstract DepoBase Class
See 451AbstractDepo project for the full text
*
Infopulse Training

Center

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How to Create and Use Library
To create depo library:
Right click on

the app package -> Export -> Java -> JAR file -> Next
JAR file = depo.jar
Finish
How you can use depo.jar library:
Create new project 451aAbstractDepo
Right click on the project name -> Build Path
-> Configure Build Path
Go to Library tab -> Add External JARs -> find and click on depo.jar -> Open -> Ok

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Interfaces
An interface is a reference type, similar to a class, that

can contain only constants, method signatures, and nested types
There are no method bodies
Interfaces cannot be instantiated—they can only be implemented by classes or extended by other interfaces

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Defining an Interface
An interface declaration consists of:
modifiers
the keyword interface

the interface name
a comma-separated list of parent interfaces (if any)
the interface body
An interface can extend any number of interfaces

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Interface Definition Example
public interface GroupedInterface extends
Interface1, Interface2, Interface3 {

// constant declarations
double E = 2.718282;
// method signatures void doSomething (int i, double x);
int doSomethingElse(String s);
}

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The Interface Body
The interface body contains method declarations for all the

methods included in the interface
A method declaration within an interface is followed by a semicolon, but no braces
All methods declared in an interface are implicitly public
An interface can contain constant declarations in addition to method declarations
All constant values defined in an interface are implicitly public, static, and final

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Use an Interface
To use an interface, you write a class that

implements the interface
When an instantiable class implements an interface, it provides a method body for each of the methods declared in the interface
public class OperateBMW760i implements GroupedInterface {
. . . .
}

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Interfaces and Multiple Inheritance
In Java, a class can inherit from only

one class but it can implement more than one interface
This means that if a variable is declared to be the type of an interface, its value can reference any object that is instantiated from any class that implements the interface

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Using an Interface as a Type
You can use interface names anywhere

you can use any other data type name
If you define a reference variable whose type is an interface, any object you assign to it must be an instance of a class that implements the interface

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Exercise: InterestInterface
Modify 442InterestSum project using interface
*
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Exercise: InterestInterface
See 452InterfaceDepo project for the full text
*
Infopulse Training Center

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Cloning (1 of 2)
Use clone() method to get independent object instead

of object’s assignment
clone() method can make only a field-by-
field copy
Cloning is correct if a class contains only primitive fields or references to immutable objects
“Deep” cloning is necessary otherwise

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Cloning (2 of 2)
The clone method is a protected method of

Object, which means that your code cannot simply call it
To make clone method accessible a class must:
Implement the Cloneable interface
Redefine the clone method with the public access modifier.

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Deep Cloning
To make a deep copy, you have clone the mutable

instance fields in the redefined clone method

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Example: DepoBase Cloning
public abstract class DepoBase implements Cloneable{
. . .

. . .
public DepoBase clone() throws CloneNotSupportedException{
DepoBase cln = (DepoBase)super.clone();
cln.startDate = (Date)startDate.clone();
return cln;
}
. . . . . .
}

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Interfaces in Java SE 8
The interface body can contain:
abstract methods (followed

by a semicolon, but no braces – it does not contain an implementation
default methods (are defined with the default modifier)
static methods (with the static keyword)
constant declarations

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Interface Default Methods
You specify that a method definition in an interface

is a default method with the default keyword at the beginning of the method signature
Default method defines a default implementation
Default methods enable you to add new functionality to the interfaces of your libraries and ensure binary compatibility with code written for older versions of those interfaces
Any class that implements the interface with default method will have this method already defined

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Exercise: Default Method
Modify 452InterfaceDepo project:
Remove abstract DepoBase class
Add calculateInterest method as

default method of the InterestInterface

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Exercise: Default Method
See 453DefaultMethod project for the full text

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Functional Interfaces
A functional interface is any interface that contains only one abstract

method
A functional interface may contain one or more default methods or static methods
The abstract method of a functional interface can be implemented with help of lambda expression

Слайд 26

Lambda Expression
A lambda expression looks a lot like a method declaration
You

can consider lambda expressions as anonymous methods—methods without a name

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Example of Lambda Expression I
public class Calculator {
interface IntegerMath {

int operation(int a, int b);
}
public int operateBinary(int a, int b, IntegerMath op) {
return op.operation(a, b);
}

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Example of Lambda Expression II
public static void main(String... args) {

Calculator myApp = new Calculator();
IntegerMath addition = (a, b) -> a + b;
IntegerMath subtraction = (a, b) -> a - b;
System.out.println("40 + 2 = " +
myApp.operateBinary(40, 2, addition));
System.out.println("20 - 10 = " +
myApp.operateBinary(20, 10, subtraction));
}
}

Слайд 29

Example of Lambda Expression
See 454LambdaCalulator for the full text

Слайд 30

Lambda Expression Syntax I
A lambda expression consists of the following:
a

comma-separated list of formal parameters enclosed in parentheses
the arrow token, ->
a body, which consists of a single expression or a statement block

Слайд 31

Lambda Expression Syntax II
You can omit the data type of the

parameters in a lambda expression
You can omit the parentheses if there is only one parameter
If you specify a single expression, then the Java runtime evaluates the expression and then returns its value
Alternatively, you must enclose statements in braces {}

4. Java OOP. 5. Abstract Classes

Содержание

Abstract ClassesAn abstract class is a class that is declared abstractAbstract

Abstract Methods An abstract method is a method that is declared

An Abstract Classes IIA subclass of an abstract class usually provides

Example: Abstract DepoBase ClassModify 442InterestSum project using DepoBase as an abstract

Example: Abstract DepoBase ClassSee 451AbstractDepo project for the full text*Infopulse Training

How to Create and Use LibraryTo create depo library:Right click on

InterfacesAn interface is a reference type, similar to a class, that

Defining an InterfaceAn interface declaration consists of: modifiers the keyword interface

Interface Definition Examplepublic interface GroupedInterface extends Interface1, Interface2, Interface3 {

The Interface BodyThe interface body contains method declarations for all the

Use an InterfaceTo use an interface, you write a class that

Interfaces and Multiple InheritanceIn Java, a class can inherit from only

Using an Interface as a TypeYou can use interface names anywhere

Exercise: InterestInterfaceModify 442InterestSum project using interface*Infopulse Training Center

Exercise: InterestInterfaceSee 452InterfaceDepo project for the full text*Infopulse Training Center

Cloning (1 of 2)Use clone() method to get independent object instead

Cloning (2 of 2)The clone method is a protected method of

Deep CloningTo make a deep copy, you have clone the mutable

Example: DepoBase Cloningpublic abstract class DepoBase implements Cloneable{ . . .

Interfaces in Java SE 8The interface body can contain:abstract methods (followed

Interface Default MethodsYou specify that a method definition in an interface

Exercise: Default MethodModify 452InterfaceDepo project:Remove abstract DepoBase classAdd calculateInterest method as

Exercise: Default MethodSee 453DefaultMethod project for the full text

Functional InterfacesA functional interface is any interface that contains only one abstract

Lambda ExpressionA lambda expression looks a lot like a method declarationYou

Example of Lambda Expression Ipublic class Calculator { interface IntegerMath {

Example of Lambda Expression II public static void main(String... args) {

Example of Lambda ExpressionSee 454LambdaCalulator for the full text

Lambda Expression Syntax IA lambda expression consists of the following: a

Lambda Expression Syntax IIYou can omit the data type of the

Похожие презентации

Abstract Classes
An abstract class is a class that is declared abstract
Abstract

Abstract Methods
An abstract method is a method that is declared

An Abstract Classes II
A subclass of an abstract class usually provides

Example: Abstract DepoBase Class
Modify 442InterestSum project using DepoBase as an abstract

Example: Abstract DepoBase Class
See 451AbstractDepo project for the full text
*
Infopulse Training

How to Create and Use Library
To create depo library:
Right click on

Interfaces
An interface is a reference type, similar to a class, that

Defining an Interface
An interface declaration consists of:
modifiers
the keyword interface

Interface Definition Example
public interface GroupedInterface extends
Interface1, Interface2, Interface3 {

The Interface Body
The interface body contains method declarations for all the

Use an Interface
To use an interface, you write a class that

Interfaces and Multiple Inheritance
In Java, a class can inherit from only

Using an Interface as a Type
You can use interface names anywhere

Exercise: InterestInterface
Modify 442InterestSum project using interface
*
Infopulse Training Center

Exercise: InterestInterface
See 452InterfaceDepo project for the full text
*
Infopulse Training Center

Cloning (1 of 2)
Use clone() method to get independent object instead

Cloning (2 of 2)
The clone method is a protected method of

Deep Cloning
To make a deep copy, you have clone the mutable

Example: DepoBase Cloning
public abstract class DepoBase implements Cloneable{
. . .

Interfaces in Java SE 8
The interface body can contain:
abstract methods (followed

Interface Default Methods
You specify that a method definition in an interface

Exercise: Default Method
Modify 452InterfaceDepo project:
Remove abstract DepoBase class
Add calculateInterest method as

Exercise: Default Method
See 453DefaultMethod project for the full text

Functional Interfaces
A functional interface is any interface that contains only one abstract

Lambda Expression
A lambda expression looks a lot like a method declaration
You

Example of Lambda Expression I
public class Calculator {
interface IntegerMath {

Example of Lambda Expression II
public static void main(String... args) {

Example of Lambda Expression
See 454LambdaCalulator for the full text

Lambda Expression Syntax I
A lambda expression consists of the following:
a

Lambda Expression Syntax II
You can omit the data type of the