Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters0%

The java.lang.Object Class: toString(), equals(), and hashCode()

Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters

Intermediate13 min read•Updated: 2026-10-22

🛡️ Encapsulation and Java's 4 Access Modifiers

Introduction

Encapsulation is the OOP mechanism of bundling data (attributes) and methods that manipulate that data into a single unit while restricting direct outside access. In Java, this is governed by 4 Access Levels.

📊 The 4 Access Modifiers Compared

Modifier	Inside Same Class	Inside Same Package	Subclasses (Different Package)	World (Everywhere)
`public`	✅ Yes	✅ Yes	✅ Yes	✅ Yes
`protected`	✅ Yes	✅ Yes	✅ Yes (via inheritance)	❌ No
(default / package-private)	✅ Yes	✅ Yes	❌ No	❌ No
`private`	✅ Yes	❌ No	❌ No	❌ No

🔒 Implementing Robust Getters and Setters

1public class BankAccount {
  // Private state prevents direct tampering:
  private String accountNumber;
  private double balance;
5 
  public BankAccount(String accNum, double initialDeposit) {
      this.accountNumber = accNum;
      setBalance(initialDeposit); // Use setter for validation
  }
10 
  // Getter
  public double getBalance() {
      return this.balance;
  }
15 
  // Setter with business invariant validation:
  public void setBalance(double amount) {
      if (amount >= 0.0) {
          this.balance = amount;
      } else {
          System.err.println("[ERROR]: Balance cannot be negative!");
      }
  }
24 
  public void deposit(double amount) {
      if (amount > 0.0) {
          this.balance += amount;
          System.out.printf("Deposited ₹%.2f. New Balance: ₹%.2f%n", amount, this.balance);
      }
  }
31}

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Modifier

Inside Same Class

Inside Same Package

Subclasses (Different Package)

World (Everywhere)

public

✅ Yes

protected

✅ Yes

✅ Yes (via inheritance)

❌ No

(default / package-private)

✅ Yes

❌ No

private

✅ Yes

❌ No

🔒 Implementing Robust Getters and Setters

1public class BankAccount {
  // Private state prevents direct tampering:
  private String accountNumber;
  private double balance;
5 
  public BankAccount(String accNum, double initialDeposit) {
      this.accountNumber = accNum;
      setBalance(initialDeposit); // Use setter for validation
  }
10 
  // Getter
  public double getBalance() {
      return this.balance;
  }
15 
  // Setter with business invariant validation:
  public void setBalance(double amount) {
      if (amount >= 0.0) {
          this.balance = amount;
      } else {
          System.err.println("[ERROR]: Balance cannot be negative!");
      }
  }
24 
  public void deposit(double amount) {
      if (amount > 0.0) {
          this.balance += amount;
          System.out.printf("Deposited ₹%.2f. New Balance: ₹%.2f%n", amount, this.balance);
      }
  }
31}

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Constructors: Default, Parameterized, and Constructor Chaining (this())

The java.lang.Object Class: toString(), equals(), and hashCode()