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  • MICHAEL MASLENKO thinks this is interesting:

The not-null assertion is the simplest and bluntest tool Kotlin gives you for dealing with a value of a nullable type. It’s represented by a double exclamation mark and converts any value to a non-null type. For null values, an exception is thrown

From

Cover of Kotlin in Action

Note

5
To resolve from Type? to Type at compile time and throw NPE if it's null at runtime