What is encapsulation in programming?

Encapsulation is a mechanism of bundling data and methods that operate on that data into a single unit (class) and hiding the internal implementation details from the outside world.

Key aspects:

• Data hiding: Class fields are usually declared as private or protected to restrict direct access from outside. Access is provided through accessor methods (getters and setters).

  public class Person {
      private String name; // Data hiding
  
      public String getName() { // Getter
          return name;
      }
  
      public void setName(String name) { // Setter
          this.name = name;
      }
  }
  

• Aggregation: Data (variables) and behavior (methods) of an object are combined within a single class.
• Access control: Encapsulation allows controlling how data can be modified or read, ensuring data integrity. For example, checks can be added in setters:

  public void setAge(int age) {
      if (age > 0) { // Check before setting value
          this.age = age;
      } else {
          System.out.println("Age must be a positive number.");
      }
  }
  

Advantages:

• Modularity: Simplifies understanding and maintaining code.
• Data protection: Prevents incorrect modification of data.
• Flexibility: Allows changing the internal implementation of a class without affecting other code that uses this class, provided the public API (accessor methods) remains unchanged.
• Reusability: Encapsulated components are easier to use in other parts of the application.

Encapsulation is one of the three fundamental principles of object-oriented programming (along with inheritance and polymorphism).