Static vs Instance Method

Java is considered one of the most modern and powerful languages, which provides developers with great opportunities to write correctly arranged, effective, and intelligible programs again and again. There is perhaps no better confusion to talk about than the one that exists regarding the difference between static vs non static methods in java.

Now, let’s discuss the difference between these two types of methods in this blog post, consider when to use them, and answer five most common questions to reinforce the knowledge.

What is an Instance Method?

An instance method is associated with an object of a class and normally works on data relative to that object. These modes are declared using the keyword def followed by the name of the mode together with self as the first parameter.

Example:

class MyClass {
    private int value;

    // Constructor
    public MyClass(int value) {
        this.value = value;
    }

    // Method to display the value
    public void displayValue() {
        System.out.println("The value is " + value);
    }

    // Main method to demonstrate usage
    public static void main(String[] args) {
        MyClass obj = new MyClass(10);
        obj.displayValue(); // Output: The value is 10
    }
}

Output: 
The value is 10

Key Characteristics:

• This is a method so it requires an instance of the class be called.
• Works on data in instance mode.
• self, in other words, points to the instance that calls for this function.

What is a Static Method in Java?

A static method in java is used with classes rather than objects of the class. It is marked by the @staticmethod decorator and has no arguments; it does not take self or cls for arguments. Class functions, which do not operate on an instance data and do not change the state of a class, are called static methods.

Example:

class MyClass {

    // Static method
    public static void greet(String name) {
        System.out.println("Hello, " + name + "!");
    }

    // Main method to demonstrate usage
    public static void main(String[] args) {
        MyClass.greet("Alice"); // Output: Hello, Alice!
    }
}

Output: 
Hello, Alice!

Key Characteristics:

• Can be instantiated and called directly to the class without creating an instance of the class.
• Does not inquire or change single- or multiple-instance data or classes.
• Best for any function that needs to be performed as part of the class strict activity.

Key Differences Between Static and Instance Methods

When to Use Each?

Let's explore when to use each type of method, focusing on the distinction between static vs non static methods in Java.

• Instance Method: Use when you need the instance of the method to interact with data of some sort.
• Static Method: Application of the method when the task it is performing does not require data tied to the instance or the class. Static methods are useful when creating a helper or a utility function.

Real-Life Use Cases for Static and Instance Methods

While it is easy to understand the theoretical difference in the nature of static and instance methods, it is much more inspiring to see the utilization of such methods in real life cases. Let’s explore practical examples:

1. Instance Methods: User Authentication

Instance methods should be used when there is object specific data like a user in a User Authentication system.

Example:

class User {
    private String username;
    private String password;

    // Constructor
    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    // Method to authenticate the user
    public boolean authenticate(String inputPassword) {
        return this.password.equals(inputPassword);
    }

    // Main method to demonstrate usage
    public static void main(String[] args) {
        User user = new User("john_doe", "securepassword123");
        System.out.println(user.authenticate("securepassword123")); // Output: true
    }
}

Output: True

Why use an instance method?

The authenticate method is based on password and it is a method that is directly tied with instance and options belong to the particular user.

2. Static Methods: Utility Functions in E-commerce

It should be noted that static methods are great for tasks where there are no dependencies on any instance or class data: taxes, discounts, etc.

Example:

class Order {

    // Static method to calculate tax
    public static double calculateTax(double amount, double taxRate) {
        return amount * taxRate;
    }

    // Main method to demonstrate usage
    public static void main(String[] args) {
        double totalTax = Order.calculateTax(100, 0.05);
        System.out.println(totalTax); // Output: 5.0
    }
}

Output: 
5.0

Why use a static method?

The calculate_tax method executes outside of any specific order. It executes an arbitrary work of general utility that can be accomplished in many settings.

3. Combining Both: A Banking System

In a banking application, instance methods deal with customer accounts, and the static methods are those which perform utility roles like Account number  validation.

Example:

class BankAccount {
    private String accountNumber;
    private double balance;

    // Constructor
    public BankAccount(String accountNumber, double balance) {
        this.accountNumber = accountNumber;
        this.balance = balance;
    }

    // Method to deposit amount
    public void deposit(double amount) {
        this.balance += amount;
    }

    // Method to withdraw amount
    public void withdraw(double amount) {
        if (amount <= this.balance) {
            this.balance -= amount;
        } else {
            System.out.println("Insufficient funds");
        }
    }

    // Static method to validate account number
    public static boolean validateAccountNumber(String accountNumber) {
        return accountNumber.length() == 10 && accountNumber.matches("\\d+");
    }

    // Getter for balance
    public double getBalance() {
        return this.balance;
    }

    // Main method to demonstrate usage
    public static void main(String[] args) {
        BankAccount account = new BankAccount("1234567890", 500);
        System.out.println(BankAccount.validateAccountNumber("1234567890")); // Output: true
        account.deposit(100);
        System.out.println(account.getBalance()); // Output: 600.0
    }
}

Output: 
600

Why combine them?

• Normal method (deposit, withdraw) handles a particular organization’s operations.
• Tasks such as account number validation, given by the static method validate_account_number() are universal and do not depend on an instance.

Conclusion

Static methods and instance methods mark a very important aspect when it comes to coding and especially coding an object-oriented code. For operations that rely on the instance of the current class, instance methods are required but, static methods make it convenient to add utilities within the class. Aim at using them to construct intelligently and sustainably structured Java programs!