Statements versus expressions

Kotlin utilizes expressions more widely than Java, so it is important to know the difference between a statement and an expression. A program is basically a sequence of statements and expressions. An expression produces a value, which can be used as part of another expression, variable assignment, or function parameter. An expression is a sequence of one or more operands (data that is manipulated) and zero or more operators (a token that represents a specific operation) that can be evaluated to a single value:

Let's review some examples of expressions from Kotlin:

Expression (produces a value)	Assigned value	Expression of type
a = true	true	Boolean
a = "foo" + "bar"	"foobar"	String
a = min(2, 3)	2	Integer
a = computePosition().getX()	Value returned by the getX method	Integer

 

Statements, on the other hand, perform an action and cannot be assigned to a variable, because they simply don't have a value. Statements can contain language keywords that are used to define classes (class...