What is null safety in Kotlin and why is it important?

Null safety is Kotlin's system to eliminate NullPointerException at compile time:\n\n1. Non-nullable Types (Default)\n• Variables cannot hold null by default\n• Example: var name: String = "John" // Cannot be null\n\n2. Nullable Types (Explicit)\n• Must explicitly allow null with ?\n• Example: var name: String? = null // Can be null\n\n3. Safe Call Operator (?.)\n• Safely access nullable properties\n• Returns null if receiver is null\n• Example: val length = name?.length\n\n4. Elvis Operator (?:)\n• Provides default value for null cases\n• Example: val length = name?.length ?: 0\n\n5. Not-null Assertion (!!)\n• Forces unwrap (use carefully)\n• Throws exception if null\n• Example: val length = name!!.length\n\n6. Safe Casting (as?)\n• Returns null if cast fails\n• Example: val str = obj as? String\n\n7. Why Important\n• Eliminates most common runtime error\n• Makes null handling explicit\n• Improves code reliability