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C # tutorial
Kotlin supports the usual logical conditions from mathematics
Kotlin supports the usual logical conditions from mathematics:
You can use these conditions to perform different actions for different decisions.
Kotlin has the following conditionals:
if
to specify a block of code to be executed, if a specified condition is trueelse
to specify a block of code to be executed, if the same condition is falseelse if
to specify a new condition to test, if the first condition is falsewhen
to specify many alternative blocks of code to be executedif..else
can be used as a
statement or as an expression (to assign a
value to a variable) in Kotlin. See
an example at the bottom of the page to better understand it.
Use if
to specify a block of code to be executed if a condition is true
.
if (condition) {
// block of code to be executed if the condition is true
}
Note that if
is in lowercase letters. Uppercase letters (If or IF) will generate an error.
In the example below, we test two values to find out if 20 is greater than
18. If the condition is true
, print some text:
if (20 > 18) {
println("20 is greater than 18")
}
We can also test variables:
val x = 20
val y = 18
if (x > y) {
println("x is greater than y")
}
Example explained
In the example above we use two variables, x and y,
to test whether x is greater than y
(using the >
operator). As x is 20, and y is 18, and we know that 20 is greater than 18, we print to the screen that "x is greater than y".
Use else
to specify a block of code to be executed if the condition is false
.
if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
val time = 20
if (time < 18) {
println("Good day.")
} else {
println("Good evening.")
}
// Outputs "Good evening."
Example explained
In the example above, time (20) is greater than 18, so the condition is false
,
so we move on to the else
condition and print to the screen "Good
evening". If the time was less than 18, the program would print "Good day".
Use else if
to specify a new condition if the first condition is false
.
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}
val time = 22
if (time < 10) {
println("Good morning.")
} else if (time < 20) {
println("Good day.")
} else {
println("Good evening.")
}
// Outputs "Good evening."
Example explained
In the example above, time (22) is greater than 10, so the first condition is false
. The next condition, in the
else if
statement, is also false
, so we move on to the else
condition since condition1 and condition2 is both false
- and print to the screen "Good
evening".
However, if the time was 14, our program would print "Good day."
In Kotlin, you can also use if..else
statements as expressions
(assign a value to a variable and return it):
val time = 20
val greeting = if (time < 18) {
"Good day."
} else {
"Good evening."
}
println(greeting)
When using if
as an expression, you must also include else
(required).
{}
when if
has only one statement:
fun main() {
val time = 20
val greeting = if (time < 18) "Good day." else "Good evening."
println(greeting)
}