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

LESSON 16: Java Operator Precedence

> Operator precedence determines the order in which the operators in an expression are evaluated.
> the operator with the highest precedence is operated first.
> the multiplication is performed before subtraction
> Example: Operator precedence

class Precedence {
public static void main(String[] args) {

int a = 10, b = 5, c = 1, result;
result = a-++c-++b;

System.out.println(result);
}
}

‼️What will be the output of the above example❓

For any suggestion : use our bot_ Learn+To+Code_bot

LESSON 17: EXCEPTION HANDLING IN JAVA

🖇 Exception handling is one of the most important feature of java programming that allows us to handle the runtime errors caused by exceptions.

✂️An Exception is an unwanted event that interrupts the normal flow of the program.

Java try and catch

The try statement allows you to define a block of code to be tested for errors while it is being executed.

The catch statement allows you to define a block of code to be executed, if an error occurs in the try block.



public class Main {
public static void main(String[ ] args) {
try {
int[] myNumbers = {1, 2, 3};
System.out.println(myNumbers[10]);//this num is not found in the array
} catch (Exception e) {
System.out.println("Something went wrong.");
}
}
}

THERE ARE 2 PRIMARY EXCEPTION TYPES:
1️⃣ Checked Exception
2️⃣ Unchecked Exception

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