Assign value to variable only if is not null - Kotlin

The operator is called Elvis Operator. It evaluates if x is not null and if that's true, assigns x to y. If it is null, it evaluates the statement after the question mark, returning immediately and therefore leaving y untouched.

Another solution if You don't want to return from function just yet:

x?.let{ y = it }

Which checks if x is non-null then passes it as the only parameter to the lambda block.

This is also a safe call in case your x is a var.