A Design Pattern is a reusable solution to common software design problems.

Elaboration:

• Three categories:
  1. Creational Patterns (e.g., Singleton, Factory).
  2. Structural Patterns (e.g., Adapter, Composite).
  3. Behavioral Patterns (e.g., Observer, Strategy).
• Helps in writing scalable and maintainable code.

Example (Singleton Pattern in Java):

public class Singleton {
    private static Singleton instance;
    
    private Singleton() {}

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

• Ensures only one instance of Singleton exists.