Explain the differences between a class and an abstract class in object-oriented programming.

Go does not have classes and abstract classes in the traditional sense like other object-oriented languages. Instead, it uses structs and interfaces.

Compared to classes and abstract classes:

• Class — a template for creating objects with state and behavior.
• Abstract class — a class that cannot be instantiated directly and can contain both implemented and abstract (unimplemented) methods.

In Go:

• Structs describe data.
• Interfaces describe behavior (a set of methods) that structs should implement.

Thus, an interface in Go can be considered similar to an abstract class, as it defines a contract without implementation.

Example:

// Interface (similar to abstract class)
type Animal interface {
    Speak() string
}

// Struct (similar to class)
type Dog struct {}

func (d Dog) Speak() string {
    return "Woof!"
}

// Usage:
var a Animal = Dog{}
fmt.Println(a.Speak()) // Outputs: Woof!

Therefore, in Go, there are no direct distinctions between classes and abstract classes; instead, composition through interfaces and structs is used.