In the Kotlin language we, by default, have to initialize each variable when it is introduced. To avoid this, the lateinit keyword can be used. Referring to a lateinit variable before it has been initialized results in a runtime exception.
然而，lateinit不能与基元类型一起使用.为什么会这样？
对于(不可为null的)对象类型，Kotlin使用null值来标记lateinit属性尚未初始化，并在访问该属性时引发相应的异常.
For primitive types, there is no such value, so there is no way to mark a property as non-initialized and to provide the diagnostics that lateinit needs to provide. (We could try to use a separate marker of some kind, but that marker would not be updated when initializing the field through reflection, which is a major use case of lateinit).
Therefore, lateinit is supported for properties of object types only.