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silambarasan rajendran
silambarasan rajendran

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

#java #programming #oops #coding

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};
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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"); } }
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Parameter: Variable in method definition (String notice) Argument: Actual value passed when calling ("Smart Meter")
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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() } }
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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 */ } }
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  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!"); } }
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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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