In what situations in Kotlin are objects used instead of classes or data classes?

In Kotlin, an object is used in the following situations:

• Singleton: when a single instance of a class is needed throughout the application. Declaring it with object guarantees that the object is created only once and is globally accessible.
• Companion objects: for creating static members inside a class.
• Anonymous objects: for creating objects without an explicit class, for example, when implementing interfaces.

Unlike a regular class, an object cannot be instantiated multiple times, and a data class is intended for storing data with automatically generated methods equals, hashCode, toString.

Example of a singleton:

object DatabaseConfig {
    val url = "jdbc:mysql://localhost:3306/mydb"
    val user = "root"
    val password = "password"

    fun connect() {
        // connection logic
    }
}

Such an object is convenient to use when you need to centrally store settings or common functions.