4 : Conditionals

    Kotlin has the familiar if-else statement that you are used to from Java and Python:

    i = 10
if (i < 11):
  print("Here")
else:
  print("There")

    Kotlin does not have a switch statement, but instead has a more powerful conditional called when:

    Without an argument when can be used to replace simple if-else chains:

    In this last form each conditional expression on the left side of each statement in when when block is evaluated until we find one that is true, or reach the else statement.

    Conditional Expressions

    Unlike Java or Python (or JavaScript), both if-else and when can be used in Kotlin as expressions—used to assign variables. This proves to be quite natural and elegant:

    Note how the example above allows us to preserve both the immutability and non-nullability of the variable grade. There is no way to accomplish this in either Java or Python. Again, since grade would need to be declared outside of the block but set inside, it would have to be mutable.

    When using if-else as an expression the last statement from each block is used to perform the assignment. But each branch of the if-else can also do other work—it doesn’t just have to return a value.

    Finally, whenever we use a conditional expression to set a variable, Kotlin will help ensure that the variable does get set by requiring an else statement: