JAVA

Methods

As programs grow larger, writing all code inside the main() method becomes difficult to manage. The same logic may need to be used multiple times in different parts of the program. Copying and pasting code leads to duplication, makes programs harder to maintain, and increases the chances of errors.

To solve this problem, Java provides methods. A method is a reusable block of code that performs a specific task. Instead of writing the same code multiple times, you can place it inside a method and call that method whenever needed.

In this chapter, you will learn how to create methods, pass data to methods, return values from methods, and organize code more effectively.

What is a Method?

A method is a named block of code that performs a specific task.

Examples of tasks a method might perform:

• Calculate a total price
• Display a welcome message
• Validate a password
• Find the largest number
• Calculate a student's grade

Once a method is created, it can be called whenever that task needs to be performed.

Why Do We Need Methods?

Consider the following program:

System.out.println("Welcome");
System.out.println("Welcome");
System.out.println("Welcome");

If the same logic is needed many times, repeating code becomes inefficient.

Using a method:

displayMessage();
displayMessage();
displayMessage();

The code becomes cleaner, easier to read, and easier to maintain.

Creating a Method

Syntax

returnType methodName() {

}

Example:

public static void greet() {
    System.out.println("Welcome to Java");
}

Here:

• public specifies the access level.
• static allows the method to be called from main().
• void means the method does not return a value.
• greet is the method name.

For now, focus mainly on the method name and the code inside the method.

Calling a Method

Creating a method does not execute it.

A method must be called.

Example

public class Main {

    public static void greet() {
        System.out.println("Welcome to Java");
    }

    public static void main(String[] args) {
        greet();
    }
}

Output

Welcome to Java

Explanation

• The method greet() is created.
• main() calls the method.
• Java executes the code inside the method.

Calling a Method Multiple Times

Example

public class Main {

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

    public static void main(String[] args) {

        greet();
        greet();
        greet();

    }
}

Output

Welcome
Welcome
Welcome

A single method can be called as many times as needed.

Methods with Parameters

Sometimes a method needs data to perform its task.

This data is passed using parameters.

Syntax

returnType methodName(parameter) {

}

Example

public static void greet(String name) {
    System.out.println("Hello " + name);
}

Calling the method:

greet("Rahul");

Output

Hello Rahul

Explanation

• name is a parameter.
• "Rahul" is passed to the method.
• The value is stored in name.
• The method uses that value while executing.

Methods with Multiple Parameters

A method can accept multiple values.

Example

public static void displayUser(String name, int age) {
    System.out.println(name);
    System.out.println(age);
}

Calling the method:

displayUser("Rahul", 18);

Output

Rahul
18

Returning Values from Methods

Some methods perform a calculation and return a result.

For this, the return statement is used.

Example

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

Calling the method:

int result = add(10, 20);

System.out.println(result);

Output

30

Explanation

• The method receives two numbers.
• It adds them together.
• The result is returned.
• The returned value is stored in result.

The void Keyword

Methods that do not return a value use the void keyword.

Example

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

This method performs an action but does not return anything.

The return Statement

The return statement immediately ends a method and sends a value back to the caller.

Example

public static int square(int number) {
    return number * number;
}

Calling:

System.out.println(square(5));

Output

25

Complete Program

Example

import java.util.Scanner;

public class Main {

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

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();

        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();

        int result = add(num1, num2);

        System.out.println("Sum = " + result);
    }
}

Input

10
20

Output

Sum = 30

Explanation

• The user enters two numbers.
• The numbers are passed to the add() method.
• The method calculates the sum.
• The result is returned.
• The returned value is displayed on the screen.

Common Mistakes

Forgetting to Call the Method

Wrong

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

The method is created but never called.

Correct

greet();

Returning the Wrong Data Type

Wrong

public static int getName() {
    return "Rahul";
}

The method is declared to return an int, but returns a String.

Correct

public static String getName() {
    return "Rahul";
}

Key Takeaways

• Methods are reusable blocks of code.
• Methods help reduce code duplication.
• A method must be called to execute.
• Parameters allow data to be passed into methods.
• Methods can return values using the return statement.
• void methods do not return anything.
• Methods make programs easier to organize, maintain, and reuse.