14_Methods

Methods

What is a Method?

A method is a code block designed to perform a specific task. It is like an instruction that tells the program to do something specific, like an action.

Think of it like giving a command to do something:

print the bill

calculate total

Login with credentials

How to define a method structure ?

returnType methodName(argument1, argument2) { // Method Signature // arguments are the local variables(stored in stack memory) passed into the methods
    
 //  What we are going to do inside the method body
}

What is a Method Signature?

Method Signature is  - Method Name + Return Type + Parameter List (argument1, argument2)**

  
    int addNumbers(int a, int b)                   // Method Name + Return Type + Parameter List (argument1, argument2)
    ↑     ↑         ↑        ↑
    |     |         |        |
 Return  |     Argument1   Argument2
  Type   |   (local var)  (local var)
         |
     Method Name

What is a Method Declaration?

What we are going to do inside the braces (code block)!

What is a Return Type ?

The return type tells us what the method will give back after execution (the type). It is specified before the method name during definition.

Let's learn from examples!

1. Method With Return Type (int)

Adding two numbers returns a number as result. So int is the return type of this method.

public int addNumbers(int a, int b) { // Adding two numbers returns a number as result. So int is the return type of this method.

    return a + b; // returns sum of two numbers (int)
}

2. Method with Return Type (String)

This method returns name which is of type String.

public String greet(String name) {

    return "Hello, " + name + "!"; // returns name which is of type String
}

3. Method with void Return Type

This method performs an action (printing), but doesn't return anything — so the return type is void.

void is a reserved keyword in java.

public void printWelcome() {.    // void is a reserved keyword in java

    System.out.println("Welcome to Java Learning Journal!"); //This method returns a String greeting message based on the input.
}

Real-Life Actions → Method Names in Java

| Real-Life Action                 | Method Name (Java)        | Return Type Example | What It Might Do                                      
|----------------------------------|---------------------------|----------------------|--------------------------------------------------------|
| Print the bill                   | printBill()               |   void               | Prints the bill to a printer or screen                |
| Calculate total price            | calculateTotal()          |    int               | Returns total after adding price + tax                |
| Show welcome message             | showWelcomeMessage()      |    void              | Displays a welcome message on screen                  |
| Check if user is logged in       | isUserLoggedIn()          |   boolean            | Returns `true` or `false` based on login status       |
| Get full name from first & last  | getFullName()             |   String             | Combines first and last name and returns full name    |
| Read input from user             | readInput()               |   String             | Reads and returns user input from console             |
| Save data to file                | saveToFile()              |   void               | Saves current data to a file                          |
| Convert Celsius to Fahrenheit    | convertTemperature()      |  `double              | Converts temp and returns the Fahrenheit value       |

Benefits of Using Methods

REUSABILITY – Write once, use many times. Avoid repeating the same logic.

READABILITY – Code becomes easier to understand and maintain.

MODULARITY – Breaks large programs into smaller, manageable pieces.

Best Practices

Keep methods small and do one task per method.

Create reusable methods to avoid redundancy.

Types of Methods

| Type             | Description                                         |
|------------------|-----------------------------------------------------|
| Static Methods   | Utility methods that belong to the class            |
| Instance Methods | Non-static methods that belong to objects           |

Utility Method - Use Cases

Reading from CSV

Taking screenshots

Connecting to a database