LESSON 11: ENCAPSULATION

✅Encapsulation is defined as the wrapping up of data under a single unit. It is the mechanism that binds together code and the data it manipulates.
Another way to think about encapsulation is, it is a protective shield that prevents the data from being accessed by the code outside this shield.
Following is an example that demonsrates how to achieve encapsualtion in java:

/* File name : EncapTest.java */

public class EncapTest {
   private String name;
   private String idNum;
   private int age;

   public int getAge() {
      return age;
   }

   public String getName() {
      return name;
   }

   public String getIdNum() {
      return idNum;
   }

   public void setAge( int newAge) {
      age = newAge;
   }

   public void setName(String newName) {
      name = newName;
   }

   public void setIdNum( String newId) {
      idNum = newId;
   }
}

// more organized source codes at: https://t.me/java_learntocode

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LESSON 12: POLYMORPHISM

The word polymorphism means having many forms. In simple words, we can define polymorphism as the ability of a message to be displayed in more than one form.

Types of polymorphism

In Java , polymorphism is mainly divided into two types:

i.Compile-time Polymorphism
💎This type of polymorphism is achieved by function overloading or operator overloading. But Java doesn’t support the Operator Overloading.

ii.Runtime Polymorphism
❤️‍🔥It is a process in which a function call to the overridden method is resolved at Runtime. This type of polymorphism is achieved by Method Overriding.

>💗 Java program to demostrate polymorphism

class Parent {
 
    // Method of parent class
    void Print()
    {
 
        // Print statement
        System.out.println("parent class");
    }
}
 

// Helper class
class subclass2 extends Parent {
 
    // Method
    void Print()
    {
 
        // Print statement
        System.out.println("subclass2");
    }
}
 
// Class 4
// Main class
class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
 
        // Creating object of class 1
        Parent a;
 
        // Now we will be calling print methods
        // inside main() method
 
        a = new subclass1();
        a.Print();
 
      
    }
}

WHAT IS THE CORRECT OUTPUT OF THE SNIPPET CODE?

BASIC CONCEPTS OF JAVA:-

LESSON 13: INHERITANCE

⚜️Inheritance is one of the basic concept in object
orientation in which a new class is created by
absorbing an existing class’s members and
embellishing them with new or modified capabilities.

✅ The existing class is called the superclass, and the
new class is the subclass.

Syntax for inheritance
class SubClassName extends SuperClassName{};

Why And When To Use "Inheritance"?

- It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class.

Let's explore by using sample code:-
class Vehicle {
protected String brand = "Ford"; // Vehicle attribute
public void honk() { // Vehicle method
System.out.println("Tuut, tuut!");
}
}

class Car extends Vehicle {
private String modelName = "Mustang"; // Car attribute
public static void main(String[] args) {

// Create a myCar object
Car myCar = new Car();

// Call the honk() method (from the Vehicle class) on the myCar object
myCar.honk();

// Display the value of the brand attribute (from the Vehicle class) and the value of the modelName from the Car class
System.out.println(myCar.brand + " " + myCar.modelName);
}
}


"thanks all!🙏"

LESSON 14: ABSTRACTION and INTERFACES
🔱 Abstraction is the property by virtue of which only the essential details are displayed to the user. The trivial or the non-essential units are not displayed to the user. Ex: A car is viewed as a car rather than its individual components


✳️An Interface in Java programming language is defined as an abstract type used to specify the behavior of a class. An interface in Java is a blueprint of a class. A Java interface contains static constants and abstract methods.

⚜️Why do we use an Interface?✅

> It is used to achieve total abstraction.
Since java does not support multiple inheritances in the case of class, by using an interface it can achieve multiple inheritances.
> It is also used to achieve loose coupling.
> Interfaces are used to implement abstraction. So the question arises why use interfaces when we have abstract classes?

What will be the output of the following program?

public class King {
public static void main(String[] args) {
King k = new King();
Elephant e = k.new Elephant();
System.out.print("Output = ");
System.out.print(e.step2(2, 3));
}
interface Queen {
float step2(int low, int high);
}
interface Pawn {
float step3(int a, int b, int c);
}
abstract class Knight implements Queen, Pawn {
}
class Elephant implements Queen {
public float step2(int x, int y) {
return 2;
}
}
}

//

LESSON 15: 📁File Class in java🗂

🔗The File class is an abstract representation of file and directory pathname. A pathname can be either absolute or relative.

📝Once you have File object in hand, then there is a list of helper methods which can be used to manipulate the files.

Eg: public String getName()
public String getParent()
public File getParentFile()
public String getPath()
public boolean isAbsolute() ... and etc.

import java.io.*;
public class LearnTcode {
public static void main(String[] args) {

try {
File file = new File("learnTocode.txt");
if (file.createNewFile()) {
System.out.println("Join our channel");
} else {
System.out.println("File already exists.");
}
} catch (IOException e) {
e.printStackTrace();
}

}
}
//output is: Join our channel