what is java? basic java programming,Object oriented programming

 

What is Java?

Java is a high-level, object-oriented programming (OOP) language developed by Sun Microsystems (now owned by Oracle). It is platform-independent, meaning Java code can run on any system that has a Java Virtual Machine (JVM). Java is known for its "Write Once, Run Anywhere" capability, strong memory management, and robustness. It is widely used in web applications, mobile apps (Android), enterprise systems, and cloud computing.

Importance of Java in Today’s Development

Java remains one of the most widely used programming languages in software development due to its reliability, security, and scalability. It is used across various domains, from web and mobile applications to enterprise systems and cloud computing. Here’s why Java is crucial in today’s development landscape:

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1. Platform Independence ("Write Once, Run Anywhere")

Java applications can run on any device or operating system that has a Java Virtual Machine (JVM). This makes Java ideal for cross-platform applications, reducing the need for platform-specific code.

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2. Strong Object-Oriented Programming (OOP) Principles

Java follows OOP principles, making development more modular, reusable, and maintainable. This is essential for building large-scale applications efficiently.

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3. Wide Use in Enterprise Applications

Java is the backbone of many large-scale enterprise applications, particularly in sectors like banking, e-commerce, and finance. Frameworks like Spring Boot and Hibernate simplify the development of robust, scalable enterprise applications.

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4. Android Development

Java is one of the primary languages used in Android app development. Though Kotlin is gaining popularity, Java remains widely used for building mobile applications.

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5. Cloud Computing & Big Data

Java is a preferred choice for cloud-based applications and Big Data technologies. Many cloud service providers support Java applications, and tools like Apache Hadoop, Apache Spark, and Kafka rely on Java.

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6. Web Development

Java powers many web applications using frameworks like Spring, Struts, and JSF. These frameworks provide high security, scalability, and performance.

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7. Security & Performance

Java provides built-in security features like bytecode verification, exception handling, and access control, making it ideal for secure applications such as banking and government systems.

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8. Strong Community & Open-Source Ecosystem

Java has a vast developer community, offering extensive libraries, frameworks, and resources. Open-source projects like Spring, Hibernate, and Maven enhance Java’s capabilities and speed up development.

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9. Scalability & Performance

Java applications can handle high loads efficiently, making it suitable for high-performance applications like stock trading platforms, e-commerce websites, and distributed systems.

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10. Artificial Intelligence & IoT

Java is increasingly used in AI, machine learning, and Internet of Things (IoT) applications due to its versatility, speed, and platform independence.

problem: write java code to take 2 inputs and do addition,substracrion,multiplication,divition

code:

import java.util.Scanner; // Import Scanner class for user input public class ArithmeticOperations { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); // Create Scanner object // Taking user input System.out.print("Enter first number: "); double num1 = scanner.nextDouble(); System.out.print("Enter second number: "); double num2 = scanner.nextDouble(); // Performing arithmetic operations double sum = num1 + num2; double difference = num1 - num2; double product = num1 * num2; double quotient = (num2 != 0) ? num1 / num2 : Double.NaN; // Handling division by zero // Displaying results System.out.println("\nResults:"); System.out.println("Addition: " + sum); System.out.println("Subtraction: " + difference); System.out.println("Multiplication: " + product); if (num2 != 0) { System.out.println("Division: " + quotient); } else { System.out.println("Division: Undefined (cannot divide by zero)"); } scanner.close(); // Close scanner } }

problem :Java program that takes the user's marks as input and assigns a grade based on a standard grading system

code:

import java.util.Scanner; public class GradeCalculator { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int marks; // Taking user input with validation do { System.out.print("Enter your marks (0-100): "); marks = scanner.nextInt(); if (marks < 0 || marks > 100) { System.out.println("Invalid input! Marks should be between 0 and 100."); } } while (marks < 0 || marks > 100); // Determine the grade using if-else char grade; if (marks >= 90) { grade = 'A'; } else if (marks >= 80) { grade = 'B'; } else if (marks >= 70) { grade = 'C'; } else if (marks >= 60) { grade = 'D'; } else if (marks >= 50) { grade = 'E'; } else { grade = 'F'; // Fail } // Display the result System.out.println("Your grade is: " + grade); scanner.close(); } }

What is Object-Oriented Programming (OOP)?

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of objects, which are instances of classes. OOP allows for better code organization, reusability, and maintainability by modeling real-world entities. The four main principles of OOP are:

1. Encapsulation – Bundling data and methods that operate on that data into a single unit (class).
2. Abstraction – Hiding complex implementation details and exposing only the necessary functionalities.
3. Inheritance – Allowing a class (child) to inherit properties and behaviors from another class (parent).
4. Polymorphism – Allowing a single interface or method to take different forms.

1. Encapsulation (Data Hiding & Access Control)

Encapsulation means wrapping data (variables) and methods into a single unit (class) and restricting direct access using access modifiers (private, public, protected).

Java Code for Encapsulation

class Student {
    private String name; // Private variable (Encapsulation)

    // Getter method to access private variable
    public String getName() {
        return name;
    }

    // Setter method to set private variable
    public void setName(String newName) {
        name = newName;
    }
}

public class EncapsulationExample {
    public static void main(String[] args) {
        Student student = new Student();
        student.setName("John Doe"); // Setting name using setter
        System.out.println("Student Name: " + student.getName()); // Getting name using getter
    }
}

Key Features:

✔ Protects data using private
✔ Provides controlled access via getter/setter methods

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2. Abstraction (Hiding Implementation Details)

Abstraction hides complex implementation details and only shows necessary functionalities using abstract classes or interfaces.

Java Code for Abstraction

abstract class Vehicle {
    abstract void start(); // Abstract method (No body)
}

class Car extends Vehicle {
    @Override
    void start() {
        System.out.println("Car is starting with a key...");
    }
}

public class AbstractionExample {
    public static void main(String[] args) {
        Vehicle myCar = new Car();
        myCar.start(); // Calls the overridden method in Car class
    }
}

Key Features:

✔ Hides internal details
✔ Uses abstract classes/methods

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3. Inheritance (Code Reusability)

Inheritance allows a child class to inherit properties and behaviors from a parent class, reducing code duplication.

Java Code for Inheritance

// Parent class
class Animal {
    void makeSound() {
        System.out.println("Animal makes a sound...");
    }
}

// Child class (inherits from Animal)
class Dog extends Animal {
    @Override
    void makeSound() {
        System.out.println("Dog barks: Woof! Woof!");
    }
}

public class InheritanceExample {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.makeSound(); // Calls overridden method in Dog class
    }
}

Key Features:

✔ Reuses existing code
✔ Uses extends keyword for inheritance

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4. Polymorphism (One Interface, Many Forms)

Polymorphism allows one method to behave differently based on the object that calls it. It can be achieved via:

• Method Overloading (Same method name, different parameters)
• Method Overriding (Child class redefines parent method)

Java Code for Polymorphism

class MathOperations {
    // Method Overloading: Multiple methods with same name but different parameters
    int add(int a, int b) {
        return a + b;
    }

    int add(int a, int b, int c) {
        return a + b + c;
    }
}

public class PolymorphismExample {
    public static void main(String[] args) {
        MathOperations obj = new MathOperations();
        System.out.println("Sum (2 numbers): " + obj.add(5, 10));
        System.out.println("Sum (3 numbers): " + obj.add(5, 10, 15));
    }
}

Key Features:

✔ Method Overloading → Same method name, different arguments
✔ Method Overriding → Child class modifies behavior

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Summary of OOP Concepts in Java

OOP Concept	Description	Java Feature Used
Encapsulation	Hides data and restricts access	Private variables & Getters/Setters
Abstraction	Hides implementation details	Abstract classes & Interfaces
Inheritance	Reuses code from parent classes	extends keyword
Polymorphism	One interface, multiple implementations	Method Overloading & Overriding