Can you tell us about the most frequently used design pattern?

One of the most commonly used design patterns is Singleton.

It guarantees that a class has only one instance and provides a global point of access to it. This is useful when you need to control access to a resource, such as configuration, logger, or connection pool.

Example in Java:

public class Singleton {
    private static Singleton instance;

    private Singleton() {
        // private constructor prevents instantiation from outside
    }

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

This pattern is simple and widely applicable, but requires caution in multithreaded environments and during testing.