EvoNext

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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

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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 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?

The Question has a mistake. the Answer is: protected and public

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!🙏"

BASIC CONCEPTS OF JAVA:-

WHAT IS THE CORRECT OUTPUT OF THE SNIPPET CODE?

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();
 
      
    }
}