Kotlin Expression, Statements and Blocks

Kotlin Expressions

Expressions consist of variables, operators etc that evaluates to a single value.

Let's take an example,

val score: Int
score = 90 + 25

Here, 90 + 25 is an expression that returns Int value.

In Kotlin, if is an expression unlike Java (In Java, if is a statement). For example,

fun main(args: Array<String>) {

    val a = 12
    val b = 13
    val max: Int

    max = if (a > b) a else b
    println("$max")
}

Here, if (a > b) a else b is an expression. Then value of the expression is assigned to max variable in the above program. Visit this page to learn more about Kotlin if expression.

Kotlin Statements

Statements are everything that make up a complete unit of execution. For example,

val score = 90 + 25

Here, 90 + 25 is an expression that returns 115, and val score = 9*5; is a statement.

Expressions are part of statements.

Some examples:

println("Howdy")

var a = 5
++a

max = if (a > b) a else b

Kotlin Blocks

A block is a group of statements (zero or more) that is enclosed in curly braces { }. For example,

fun main(args: Array<String>) {  // main function block
    val flag = true

    if (flag == true) {      // start of if block
        print("Hey ")
        print("jude!")
    }                        // end of if block
}                            // end of main function block

There are two statements print("Hey ") and print(" jude!") inside if branch block.

print("Hey ")
print("jude!")

Similarly, the main() function also has a block body.

val flag = true

if (flag == true) {      // start of block
    print("Hey ")
    print("jude!")
}                        // end of block