day-17: Java Fundamentals: Variables, Methods, and Polymorphism

Variables in Java:

1. Primitive Data Types
Data Type   Default Value   Example
int 0   int age = 25;
double  0.0 double price = 19.99;
boolean false   boolean isActive = true;
char    '\u0000'    char grade = 'A';

2. Reference Data Types
Data Type   Default Value   Example
String  null    String name = "John";
Arrays  null    int[] numbers = {1, 2, 3};

Methods in Java

Methods are blocks of code that perform specific tasks.

Parameters vs. Arguments

public class EB_Assessment {
    // 'notice' is a parameter (defined in method)
    public void reading(String notice) {
        System.out.println(notice);
    }

    public static void main(String[] args) {
        EB_Assessment meter = new EB_Assessment();
        // "Smart Meter" is an argument (passed when calling)
        meter.reading("Smart Meter"); 
    }
}

Parameter: Variable in method definition (String notice)

Argument: Actual value passed when calling ("Smart Meter")

Method Overloading

Same method name but different parameters:

class Calculator {
    // Adds two numbers
    public void add(int a, int b) {
        System.out.println(a + b);
    }

    // Adds three numbers (Overloaded)
    public void add(int a, int b, int c) {
        System.out.println(a + b + c);
    }

    public static void main(String[] args) {
        Calculator calc = new Calculator();
        calc.add(10, 20);       // Calls first add()
        calc.add(10, 20, 30);   // Calls second add()
    }
}

Key Points:
Must change number/type of parameters
Return type alone doesn't qualify as overloading

Polymorphism in Java

"Same method name, different implementations."
1). Method Overloading (Compile-Time Polymorphism)

class Printer {
    void print(String text) { /* Print text */ }
    void print(String text, int copies) { /* Print multiple copies */ }
}

1. Method Overriding (Runtime Polymorphism)

class Animal {
    void sound() { System.out.println("Animal sound"); }
}

class Dog extends Animal {
    @Override
    void sound() { System.out.println("Bark!"); }
}

Key Differences
Concept Method Overloading Method Overriding
Definition Same name, different parameters Subclass redefines parent method
Binding Compile-time Runtime
Inheritance Not required Required

Note: The formatting and structure were optimized for clarity with AI assistance.

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