Skip to content

05-Methods.md

Latest commit

 

History

History
174 lines (148 loc) · 4.03 KB

05-Methods.md

File metadata and controls

174 lines (148 loc) · 4.03 KB
Raw

Methods

1️⃣ What are Methods in Java?

A method in Java is a block of code that performs a specific task. It helps in:
✔ Code Reusability → Write once, use multiple times.
✔ Modularity → Divides the program into smaller, manageable parts.
✔ Readability → Makes the code cleaner and easier to understand.

2️⃣ Types of Methods in Java

Java has two types of methods:
1️⃣ Predefined Methods → Built-in methods (e.g., Math.sqrt(), System.out.println()).
2️⃣ User-Defined Methods → Methods created by the programmer.

3️⃣ Creating a User-Defined Method

Syntax:

returnType methodName(parameters) {
    // Method body
    return value; // Optional, required if returnType is not void
}

Example: A Simple Method

public class MethodExample {
    // Method that prints a message
    static void sayHello() {
        System.out.println("Hello, Java!");
    }

    public static void main(String[] args) {
        sayHello();  // Calling the method
    }
}

Output:

Hello, Java!

4️⃣ Method Parameters and Return Type

1. Method with Parameters

A method can accept parameters (inputs) to work with.

public class SumCalculator {
    // Method with parameters
    static void addNumbers(int a, int b) {
        int sum = a + b;
        System.out.println("Sum: " + sum);
    }

    public static void main(String[] args) {
        addNumbers(5, 10);  // Passing arguments 5 and 10
    }
}

Output:

Sum: 15

2. Method with Return Value

A method can return a value using the return keyword.

public class SquareCalculator {
    // Method that returns a value
    static int square(int num) {
        return num * num;
    }

    public static void main(String[] args) {
        int result = square(4);  // Calling the method
        System.out.println("Square: " + result);
    }
}

Output:

Square: 16

3. Method Overloading (Same method name, different parameters)

public class MethodOverloading {
    // Method to add two integers
    static int add(int a, int b) {
        return a + b;
    }

    // Method to add three integers
    static int add(int a, int b, int c) {
        return a + b + c;
    }

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

Output:

Sum (2 numbers): 15  
Sum (3 numbers): 30

5️⃣ Static vs Non-Static Methods

1. Static Methods

  • Belong to the class, not an object.
  • Called using the class name.
public class StaticExample {
    // Static method
    static void showMessage() {
        System.out.println("This is a static method!");
    }

    public static void main(String[] args) {
        StaticExample.showMessage();  // Calling without creating an object
    }
}

2. Non-Static Methods

  • Belong to an object of the class.
  • Need an object to be called.
public class NonStaticExample {
    // Non-static method
    void showMessage() {
        System.out.println("This is a non-static method!");
    }

    public static void main(String[] args) {
        NonStaticExample obj = new NonStaticExample();  // Creating an object
        obj.showMessage();  // Calling method using the object
    }
}

6️⃣ Recursion in Java (Method Calling Itself)

A recursive method calls itself to solve a problem.

Example: Factorial Using Recursion

public class RecursionExample {
    // Recursive method to calculate factorial
    static int factorial(int n) {
        if (n == 1) return 1;  // Base case
        return n * factorial(n - 1);  // Recursive call
    }

    public static void main(String[] args) {
        System.out.println("Factorial of 5: " + factorial(5));
    }
}

Output:

Factorial of 5: 120