Why encapsulation is required in Java - See It in Action

Why Encapsulation is Required in Java

📖 Scenario: Imagine you are building a simple bank account system. You want to keep the account balance safe so that no one can change it directly without following the rules.

🎯 Goal: You will create a Java class that uses encapsulation to protect the account balance. You will see why encapsulation is important by controlling how the balance is accessed and changed.

📋 What You'll Learn

Create a class called BankAccount with a private variable balance of type double

Add a public method getBalance() to return the current balance

Add a public method deposit(double amount) to add money to the balance only if the amount is positive

Add a public method withdraw(double amount) to subtract money from the balance only if the amount is positive and less than or equal to the balance

Create a main method to test the BankAccount class by depositing and withdrawing money and printing the balance

💡 Why This Matters

🌍 Real World

Banking systems and many software use encapsulation to protect sensitive data like account balances or personal information.

💼 Career

Understanding encapsulation is essential for writing secure and maintainable code in professional Java development.

1

Create the BankAccount class with a private balance

Create a class called BankAccount with a private double variable named balance initialized to 0.

Java

public class BankAccount {
    // Your code here
}

Need a hint?

Use private double balance = 0; inside the class to keep the balance hidden.

2

Add public methods to get balance and deposit money

Add a public method getBalance() that returns balance. Add a public method deposit(double amount) that adds amount to balance only if amount is greater than 0.

Java

public class BankAccount {
    private double balance = 0;

    // Your code here
}

Need a hint?

Use if (amount > 0) to check the deposit amount before adding it.

3

Add a withdraw method with checks

Add a public method withdraw(double amount) that subtracts amount from balance only if amount is greater than 0 and less than or equal to balance.

Java

public class BankAccount {
    private double balance = 0;

    public double getBalance() {
        return balance;
    }

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    // Your code here
}

Need a hint?

Check both that amount is positive and does not exceed balance before subtracting.

4

Test the BankAccount class in main method

Create a main method inside BankAccount. Create an object account of BankAccount. Deposit 100, withdraw 30, then print the balance using System.out.println(account.getBalance()).

Java

public class BankAccount {
    private double balance = 0;

    public double getBalance() {
        return balance;
    }

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public void withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
        }
    }

    // Your code here
}

Need a hint?

Use System.out.println(account.getBalance()) to show the final balance.