Explain null safety in Kotlin with examples.

Kotlin eliminates NullPointerException by distinguishing nullable and non-nullable types. Non-nullable: var name: String = "John" (cannot be null), Nullable: var name: String? = null (can be null). Safe call operator: name?.length, Elvis operator: name?.length ?: 0, Not-null assertion: name!!.length (throws exception if null). This prevents runtime crashes from null references.