Презентация на тему Java. Inheritance

behavior is known as an object. For example: chair,

pen, table, keyboard, bike etc. It can be physical and logical.
Class
Collection of objects is called class. It is a logical entity.
Inheritance
When one object acquires all the properties and behaviors of parent object i.e. known as inheritance. It provides code reusability. It is used to achieve runtime polymorphism.
Polymorphism
When one task is performed by different ways i.e. known as polymorphism. For example: cat speaks meow, dog barks woof etc.

is known as an abstraction. For example: phone call,

we don't know the internal processing.
In java, we use abstract class and interface to achieve abstraction.
Encapsulation
Binding (or wrapping) code and data together into a single unit is known as encapsulation. For example: capsule, it is wrapped with different medicines.
A java class is the example of encapsulation. Java bean is the fully encapsulated class because all the data members are private here.

need to forbid creating instances of this class.
Abstract class

may has one or more abstract methods.
A method is declared abstract when it has a method heading, but no body – which means that an abstract method has no implementation code inside curly braces like normal methods do.
The derived class must provide a definition method;
The derived class must be declared abstract itself.
A non abstract class is called a concrete class.

Abstract Classes

abstract because it contains an abstract method */
public abstract

class Figure {
/* because this is an abstract
method the body will be blank */
public abstract double getArea();
}

public class Circle extends Figure {
private double radius;
public Circle (double radius) {
this.radius = radius;}
public double getArea() {
return (3.14 * (radius * 2)); }
}

Abstract Classes

length, width;

public class Rectangle(double length, double width) {

this.length = lengt;
this.width = width;
}

public double getArea() {
return length * width;
}
}

Abstract Classes

it is similar to class, it is a collection

of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.
Along with abstract methods an interface may also contain constants, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods.
An interface is essentially a type that can be satisfied by any class that implements the interface.
Any class that implements an interface must satisfy 2 conditions
It must have the phrase "implements Interface_Name" at the beginning of the class definiton;
It must implement all of the method headings listed in the interface definition.

Interfaces

class SomeClass implements Dog {
public boolean barks() {

// method definition here
}
public boolean isGoldenRetriever() {
// method definition here
}
}

Interfaces

implementations to interfaces by utilizing the default keyword. This

feature is also known as Extension Methods.
For example:
interface Formula {
double calculate(int a);

default double sqrt(int a) {
return Math.sqrt(a);
}
}

Default Methods for Interfaces

the default method sqrt. Concrete classes only have to implement

the abstract method calculate. The default method sqrt can be used out of the box.

Formula formula = new Formula() {
@Override
public double calculate(int a) {
return sqrt(a * 100);
}
};

formula.calculate(100); // 100.0
formula.sqrt(16); // 4.0

Default Methods for Interfaces

data = 1.0;
data = num; // num = data;

???

class Aclass {
int field1 = 10;
}

class Bclass extends Aclass {
int field2 = 20;
}

Aclass a = new Aclass( );
Bclass b = new Bclass( );
a = b; // b = a; ???

Inheritance

Constructors
public Circle() {
this.radius = 1.0;

}
public Circle(double radius) {
this.radius = radius; }

// Getters and Setters
// Return the area of this Circle
public double getArea() {
return radius * radius * Math.PI;
}
}

// Constructors
public Cylinder() {

super(); // invoke superclass' constructor Circle()
this.height = 1.0;
}
public Cylinder(double height) {
super(); // invoke superclass' constructor Circle()
this.height = height;
}
public Cylinder(double height, double radius) {
// invoke superclass' constructor Circle(radius)
super(radius);
this.height = height;
}

Return the volume of this Cylinder
public double

getVolume() {
// Use Circle's getArea()
return getArea() * height;
}

// Describle itself
public String toString() {
return "This is a Cylinder";
}
}

void m1() {
System.out.println("ClassA, metod m1, i = " +

i); }
public void m2() {
System.out.println("ClassA, metod m2, i = " + i); }
public void m3() {
System.out.print("ClassA, metod m3,
runnind m4():"); m4(); }
public void m4() {
System.out.println("ClassA, metod m4");
}
}

Inheritance

double i = 1.1;
public void m1() {
System.out.println("ClassB,

metod m1, i= " + i);
}
public void m4() {
System.out.println("ClassB, metod m4");
}
}
Automatically added default constructor.

Inheritance

{

System.out.println("The Start.");

ClassA a = new

ClassA();
System.out.println("Test ClassA.");
a.m1();
a.m2();
a.m3();
a.m4();

Inheritance

System.out.println("Test ClassB.");
b.m1();
b.m2();
b.m3();

b.m4();

ClassA b0 = new ClassB();
System.out.println("Test_0 ClassB.");
b0.m1();
b0.m2();
b0.m3();
b0.m4();
System.out.println("The End."); } }

Inheritance

i=1
ClassA, metod m3, runnind m4(): ClassA, metod m4
ClassA, metod

m4
Test ClassB.
ClassB, metod m1, i=1.1
ClassA, metod m2, i=1
ClassA, metod m3, runnind m4(): ClassB, metod m4
ClassB, metod m4
Test_0 ClassB.
ClassB, metod m1, i=1.1
ClassA, metod m2, i=1
ClassA, metod m3, runnind m4(): ClassB, metod m4
ClassB, metod m4
The End.

Inheritance

com.softserve.train; public class Parent {
int f( ) {

return 1; }
public int useF() { return f(); }
}

package com.softserve.train2; import com.softserve.train.Parent;
public class Child extends Parent {
int f() { return 2; } }

public static void main(String... args) {

Child child = new Child(); System.out.println(child.useF()); } }

maxSpeed;

public double getMaxSpeed( ) {

return maxSpeed;
}

public void setMaxSpeed(double maxSpeed) {
this.maxSpeed = maxSpeed;
}

abstract void carRides( );
}

Polymorphism

BmwX6( ) { }

@Override
public void

carRides( ) {
setMaxSpeed(200);
System.out.println("Car Rides");
workedEngine( );
workedGearBox( );
}
public void workedEngine( ) {
System.out.println("BmwX6: Engine Running
on Petrol.");
System.out.println("BmwX6: Max Speed: " +
getMaxSpeed( ));
}

Polymorphism

System.out.println("BmwX6: Worked GearBox.");
}

public void lightsShine( )

{
System.out.println("BmwX6: Halogen Headlights.");
}
}

inheritance of private fields and methods ?

Polymorphism

BmwX6mod( ) {
super( );

}
@Override
public void workedEngine( ) {
System.out.println("BmwX6mod: Engine
Running on Diesel.");
System.out.println("BmwX6mod: Max Speed: " +
getMaxSpeed( ));
}
@Override
public void lightsShine( ) {
System.out.println("BmwX6mod: Xenon Headlights.");
super.lightsShine();
}
}

Polymorphism

main(String[ ] args) {
ACar carX6

= new BmwX6( );
carX6.carRides( );
((BmwX6)carX6).lightsShine( );

ACar carX6mod = new BmwX6mod( );
carX6mod.carRides( );
((BmwX6)carX6mod).lightsShine( );

BmwX6 carX6mod2 = new BmwX6mod( );
carX6mod2.carRides( );
carX6mod2.lightsShine( );
}
}

Polymorphism

relationships.

association -- a relationship between instances of the two

classes. There is an association between two classes if an instance of one class must know about the other in order to perform its work. In a diagram, an association is a link connecting two classes.

aggregation -- an association in which one class belongs to a collection. An aggregation has a diamond end pointing to the part containing the whole. In our diagram, Order has a collection of OrderDetails.

generalization -- an inheritance link indicating one class is a superclass of the other. A generalization has a triangle pointing to the superclass. Payment is a superclass of Cash, Check, and Credit.

value cannot be modified once assigned. 
Constants are variables defined

final double RADIUS = 10;

A final method cannot be overridden by subclasses
public final void myFinalMethod() {...}

A final class cannot extend
public final class MyFinalClass {...}

feed(). Create two classes Cat and Dog, which implement

this interface. Create array of Animal and add some Cats and Dogs to it. Call voice() and feed() method for all of it

Create next structure. In abstract class Person with property name, declare abstract method print(). In other classes in body of method print() output text “I am a …”. In class Staff declare abstract method salary(). In each concrete class create constant TYPE_PERSON. Output type of person in each constructors. Create array of Person and add some Teachers, Cleaners and Students to it. Call method print() for all of it. Call method salary() for all Teachers and Cleaner

Beginners": https://www.udemy.com/java-tutorial/
Complete lessons 26-31:

layEggs and an abstarct method fly().  Develop classes FlyingBird

and NonFlyingBird. Create class Eagle, Swallow, Penguin and Chicken.
Create array Bird and add different birds to it.
Call fly() method for all
of it. Output the
information about
each type of
created bird.

base class Employee with a string variable employeeld. Create

two classes SalariedEmployee and ContractEmployee, which implement interface and are inherited from the base class.
Describe hourly paid workers in the relevant classes (one of the children), and fixed paid workers (second child).
Describe the string variable socialSecurityNumber in the class SalariedEmployee .
Include a description of federalTaxIdmember in the class of contractEmployee .
The calculation formula for the "time-worker“ is: "the average monthly salary = hourly rate * number of hours worked"

is: "the average monthly salary = fixed monthly payment“
Create

an array of employees and add the employees with different form of payment.
Arrange the entire sequence of workers descending the average monthly wage. Output the employee ID, name, and the average monthly wage for all elements of the list.