Private data members in Java - Mini Project: Build & Apply

Understanding Private Data Members in Java

📖 Scenario: You are creating a simple Java class to represent a bank account. To keep the account details safe, you will use private data members.

🎯 Goal: Build a Java class with private data members and learn how to access them safely.

📋 What You'll Learn

Create a class with private data members

Add a constructor to initialize the data members

Add public methods to access the private data members

Print the values of the private data members using the public methods

💡 Why This Matters

🌍 Real World

Private data members are used in real-world applications to protect sensitive information like bank account details, passwords, and personal data.

💼 Career

Understanding private data members and encapsulation is essential for writing secure and maintainable code in software development jobs.

1

Create the BankAccount class with private data members

Create a class called BankAccount with two private data members: accountNumber of type String and balance of type double.

Java

public class BankAccount {
    // Your code here
}

Need a hint?

Use the private keyword before the data member declarations.

2

Add a constructor to initialize the private data members

Add a public constructor to the BankAccount class that takes two parameters: String accountNumber and double balance. Inside the constructor, set the private data members this.accountNumber and this.balance to the parameter values.

Java

public class BankAccount {
    private String accountNumber;
    private double balance;

    // Add constructor here
    // Your code here
}

Need a hint?

Use this keyword to refer to the current object's data members.

3

Add public getter methods to access private data members

Add two public methods to the BankAccount class: getAccountNumber() that returns a String and getBalance() that returns a double. These methods should return the values of the private data members accountNumber and balance respectively.

Java

public class BankAccount {
    private String accountNumber;
    private double balance;

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

    // Add getter methods here
    // Your code here
}

Need a hint?

Getter methods allow safe access to private data members.

4

Create a main method to print the private data members using getters

Add a main method inside the BankAccount class. Inside main, create a BankAccount object with accountNumber "12345" and balance 1000.50. Then print the account number and balance using the getAccountNumber() and getBalance() methods.

Java

public class BankAccount {
    private String accountNumber;
    private double balance;

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

    public String getAccountNumber() {
        return accountNumber;
    }

    public double getBalance() {
        return balance;
    }

    public static void main(String[] args) {
        // Your code here
    }
}

Need a hint?

Use System.out.println to print the values returned by the getter methods.