KOTLIN: When Expression - Revision history

Onnowpurbo: /* Kotlin when with block of code */

2022-07-24T03:10:58Z

Kotlin when with block of code

Onnowpurbo: /* Expression in when Conditions */

2022-07-24T03:08:14Z

Expression in when Conditions

Onnowpurbo at 03:06, 24 July 2022

2022-07-24T03:06:50Z

Onnowpurbo at 02:59, 22 July 2022

2022-07-22T02:59:16Z

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Onnowpurbo: Created page with "Sumber: https://www.tutorialspoint.com/kotlin/kotlin_when_expression.htm Consider a situation when you have large number of conditions to check. Though you can use if..else i..."

2022-07-18T01:12:09Z

Created page with "Sumber: https://www.tutorialspoint.com/kotlin/kotlin_when_expression.htm Consider a situation when you have large number of conditions to check. Though you can use if..else i..."

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Sumber: https://www.tutorialspoint.com/kotlin/kotlin_when_expression.htm

Consider a situation when you have large number of conditions to check. Though you can use if..else if expression to handle the situation, but Kotlin provides when expression to handle the situation in nicer way. Using when expression is far easy and more clean in comparison to writing many if...else if expressions. Kotlin when expression evaluates a section of code among many alternatives as explained in below example.

Kotlin when matches its argument against all branches sequentially until some branch condition is satisfied.

Kotlin when expression is similar to the switch statement in C, C++ and Java.
Example
fun main(args: Array<String>) {
val day = 2

val result = when (day) {
1 -> "Monday"
2 -> "Tuesday"
3 -> "Wednesday"
4 -> "Thursday"
5 -> "Friday"
6 -> "Saturday"
7 -> "Sunday"
else -> "Invalid day."
}
println(result)
}
When you run the above Kotlin program, it will generate the following output:

Tuesday
Kotlin when as Statement
Kotlin when can be used either as an expression or as a statement, simply like a switch statement in Java. If it is used as an expression, the value of the first matching branch becomes the value of the overall expression.

Example
Let's write above example once again without using expression form:

fun main(args: Array<String>) {
val day = 2

when (day) {
1 -> println("Monday")
2 -> println("Tuesday")
3 -> println("Wednesday")
4 -> println("Thursday")
5 -> println("Friday")
6 -> println("Saturday")
7 -> println("Sunday")
else -> println("Invalid day.")
}
}
When you run the above Kotlin program, it will generate the following output:

Tuesday
Combine when Conditions
We can combine multiple when conditions into a single condition.

Example
fun main(args: Array<String>) {
val day = 2

when (day) {
1, 2, 3, 4, 5 -> println("Weekday")
else -> println("Weekend")
}
}
When you run the above Kotlin program, it will generate the following output:

Weekday
Range in when Conditions
Kotlin ranges are created using double dots .. and we can use them while checking when condition with the help of in operator.

Example
fun main(args: Array<String>) {
val day = 2

when (day) {
in 1..5 -> println("Weekday")
else -> println("Weekend")
}
}
When you run the above Kotlin program, it will generate the following output:

Weekday
Expression in when Conditions
Kotlin when can use arbitrary expressions instead of a constant as branch condition.

Example
fun main(args: Array<String>) {
val x = 20
val y = 10
val z = 10

when (x) {
(y+z) -> print("y + z = x = $x")
else -> print("Condition is not satisfied")
}
}
When you run the above Kotlin program, it will generate the following output:

y + z = x = 20
Kotlin when with block of code
Kotlin when braches can be put as block of code enclosed within curly braces.

Example
fun main(args: Array<String>) {
val day = 2

when (day) {
1 -> {
println("First day of the week")
println("Monday")
}
2 -> {
println("Second day of the week")
println("Tuesday")
}
3 -> {
println("Third day of the week")
println("Wednesday")
}
4 -> println("Thursday")
5 -> println("Friday")
6 -> println("Saturday")
7 -> println("Sunday")
else -> println("Invalid day.")
}
}
When you run the above Kotlin program, it will generate the following output:

Second day of the week
Tuesday
Quiz Time (Interview & Exams Preparation)
Q 1 - Which of the following is true about Kotlin when expression?

A - It is used to compare a single value against multiple conditions

B - Kotlin when expression can be used in place of if..else if expression

C - Kotlin when branches can be integer, string, array or ranges

D - All of the above

Q 2 - Kotlin when can be used as an expression as well as a statement?

A - True

B - False

Q 3 - Kotlin when is inspired by which of the following Java statement

A - switch statement

B - if statement

C - do...while statement

C - None of the above

==Referensi==

* https://www.tutorialspoint.com/kotlin/kotlin_when_expression.htm

@@ Line 6: / Line 6: @@
 Kotlin when expression is similar to the switch statement in C, C++ and Java.
 ===Example===
@@ Line 26: / Line 35: @@
 When you run the above Kotlin program, it will generate the following output:
   Tuesday
@@ Line 32: / Line 43: @@
 Kotlin when can be used either as an expression or as a statement, simply like a switch statement in Java. If it is used as an expression, the value of the first matching branch becomes the value of the overall expression.
 ===Example===
 Let's write above example once again without using expression form:
   fun main(args: Array<String>) {
@@ Line 53: / Line 69: @@
 When you run the above Kotlin program, it will generate the following output:
   Tuesday
@@ Line 59: / Line 77: @@
 We can combine multiple when conditions into a single condition.
 ===Example===
@@ Line 72: / Line 93: @@
 When you run the above Kotlin program, it will generate the following output:
   Weekday
@@ Line 78: / Line 102: @@
 Kotlin ranges are created using double dots .. and we can use them while checking when condition with the help of in operator.
 ===Example===
@@ Line 91: / Line 117: @@
 When you run the above Kotlin program, it will generate the following output:
   Weekday

@@ Line 153: / Line 153: @@
 Kotlin when braches can be put as block of code enclosed within curly braces.
 ===Example===
@@ Line 181: / Line 183: @@
 When you run the above Kotlin program, it will generate the following output:
   Second day of the week

@@ Line 126: / Line 126: @@
 Kotlin when can use arbitrary expressions instead of a constant as branch condition.
 ===Example===
@@ Line 141: / Line 144: @@
 When you run the above Kotlin program, it will generate the following output:
   y + z = x = 20