Update 1.Kotlin_简介&变量&类&接口.md

KotlinCourse/1.Kotlin_简介&变量&类&接口.md

@@ -394,6 +394,10 @@ class Test{
 那lateinit有什么用呢？ 每次使用还要判断isInitialized。 
 The primary use-case for lateinit is when you can't initialize a property in the constructor but can guarantee that it's initialized "early enough" in some sense that most uses won't need an isInitialized check. E.g. because some framework calls a method initializing it immediately after construction.
 
+Lateinit Initialization is used when you want to initialize a variable at a later stage, especially when it's non-null and must be initialized before use.
+It's commonly used in dependency injection and testing.
+
+
 
 除了使用`lateinit`外还可以使用`by lazy {}`效果是一样的：   
 ```kotlin
@@ -417,7 +421,8 @@ test is not null haha
 
 - `by lazy{}`只能用在`val`类型而`lateinit`只能用在`var`类型
 - `lateinit`不能用在可空的属性上和`java`的基本类型上,否则会报`lateinit`错误   
-
+- lateinit在分配之前不会初始化变量，而by lazy在第一次访问时初始化它。
+- 如果在初始化之前访问，lateinit会抛出异常，而lazy则可以确保已初始化。
 lazy的背后是接收一个lambda并返回一个Lazy<T>实例的函数，第一次访问该属性时，会执行lazy对应的Lambda表达式并记录结果，后续访问该属性时只是返回记录的结果。
 
 另外系统会给lazy属性默认加上同步锁，也就是LazyThreadSafetyMode.SYNCHRONIZED，它在同一时刻只允许一个线程对lazy属性进行初始化，所以它是线程安全的。