1. Introduction to Methods

1.1 What is a Method

A method is a block of code that performs a specific task and can be reused whenever needed.

1.2 Importance of Methods

Reduces code repetition
Improves readability
Makes debugging easier

1.3 Advantages

Code reusability
Modularity
Better organization

1.4 Real-World Analogy

A method is like a machine: you give input, it processes it, and gives output.

2. Method Declaration and Definition

2.1 Syntax

returnType methodName(parameters) {
    // method body
}

2.2 Components

Access modifier (public, private)
Return type (int, void, etc.)
Method name
Parameters
Method body

2.3 Example

public static void greet() {
    System.out.println("Hello!");
}

2.4 Calling a Method

greet();

2.5 Static vs Non-Static

Static → called without object
Non-static → requires object

3. Method Parameters

3.1 What are Parameters

Parameters are inputs passed to methods.

3.2 Example

public static void add(int a, int b) {
    System.out.println(a + b);
}

3.3 Calling with Arguments

add(5, 3);

3.4 Pass by Value

Java always passes values, not references.

3.5 Multiple Parameters

You can pass multiple values:

multiply(int x, int y, int z);

4. Return Types

4.1 What is Return Type

Specifies what a method returns.

4.2 void Method

public static void show() {
    System.out.println("No return value");
}

4.3 Non-void Method

public static int sum(int a, int b) {
    return a + b;
}

4.4 Returning Values

int result = sum(5, 3);

4.5 Multiple Values

Use arrays or objects.

5. Method Overloading

5.1 Definition

Method overloading means having multiple methods with the same name but different parameters.

5.2 Example

public static int add(int a, int b) {
    return a + b;
}public static double add(double a, double b) {
    return a + b;
}

5.3 Rules

Must differ in parameters
Return type alone is not enough

5.4 Benefits

Improves readability
Reuse method names

6. Recursion

6.1 What is Recursion

A method calling itself is called recursion.

6.2 Base Case

Stops the recursion.

6.3 Example (Factorial)

public static int factorial(int n) {
    if (n == 1) {
        return 1;
    }
    return n * factorial(n - 1);
}

6.4 How it Works

Function calls itself
Keeps reducing problem
Stops at base case

6.5 Example (Fibonacci)

public static int fib(int n) {
    if (n <= 1) return n;
    return fib(n-1) + fib(n-2);
}

6.6 Advantages

Simple and clean code
Good for problems like trees

6.7 Disadvantages

Can be slower
Uses more memory

6.8 Recursion vs Loop

Recursion → function calls
Loop → iteration

Conclusion

Methods are one of the most powerful features in Java. They help break programs into smaller, reusable parts, making code easier to write, understand, and maintain. Concepts like parameters, return types, overloading, and recursion are essential for building efficient Java applications.

Methods in Java