How do the lazy and lateinit properties differ in Kotlin, and in which cases are their use most appropriate?

In Kotlin, lazy and lateinit are mechanisms for deferred initialization, but they have different uses and limitations:

• lazy is used for read-only properties (val). Initialization occurs upon the first access to the property. It is thread-safe by default.

  val myValue: String by lazy {
      println("Initialization")
      "Hello"
  }
  

• lateinit is applied only to mutable properties (var) and only to non-nullable types (usually objects). It allows declaring a property without initialization in the constructor but guarantees it will be initialized before use. Accessing it before initialization will throw an exception.

  lateinit var myString: String
  
  fun setup() {
      myString = "Initialized"
  }
  

When to use:

• lazy — when the value is expensive to compute and you want to delay initialization until the first use, and the property is immutable.
• lateinit — when the property cannot be initialized at object creation but will definitely be initialized later, and it is mutable.

lateinit cannot be used with primitive types and val.

Thus, the choice depends on the property type and initialization logic.