Kotlin basics : Looping mechanisms
Contants |
|---|
While Loop |
doWhile Loop |
For Loop |
Using BREAK and CONTINUE in looping |
Using custom label for the loop |
Usage of when construct |
- We use this construct to execute iterate a collection of elements until a condition is met
- We use the while looop when we are not sure how many loops are needed until a condition is met
- Thus we set a condition
private fun initiate() {
// List of cities
var cityList = listOf("Bangalore","Delhi","Chennai","Calcutta")
executeWhileLoop(cityList)
}
private fun executeWhileLoop(cityList: List<String>) {
var i=0
while (i<cityList.size-1){
println(cityList[i])
i++
}
}- We use the doWhile loop when we are not sure how many loops are needed until a condition is met.
- Thus we set a condition
- This is the same as the do-while loop but here we execute the statements and then check the condition, which is in reverse order for doWhile loop.
private fun initiate() {
// List of cities
var cityList = listOf("Bangalore","Delhi","Chennai","Calcutta")
executeDoWhileLoop(cityList)
}
private fun executeDoWhileLoop(cityList: List<String>) {
var i=0
do {
println(cityList[i])
i++
}while (i<cityList.size-1)
}
}- We use the for a loop when we know the number of iterations we need to perform.
- We use the range for this purpose.
private fun initiate() {
// List of cities
var cityList = listOf("Bangalore","Delhi","Chennai","Calcutta")
executeForLoop(cityList)
}
private fun executeForLoop(cityList: List<String>) {
for (city: String in cityList){
println(city)
}
}
}-
continueis a keyword used to skip execution of current iteration from the line it is mentioned in the loop. -
breakis a keyword used to skio execution of all left over iteration from the line it is mentioned int he loop.
- We can assign a custom name as a tag for a loop and can refer to this label and use it to break the loop.
- This is very useful in multidimensional or nested looping mechanism.
private fun initiate() {
// List of cities
var cityList = listOf("Bangalore","Delhi","Chennai","Calcutta")
usingLabel(cityList)
}
private fun usingLabel(cityList: List<String>) {
myLabel@for (city: String in cityList){
if (city == "Calcutta"){
break@myLabel
}else{
println(city)
}
}
}- we use this when we need to evaluate multiple expressions
// STRUCTURE
when(value) {
expression1 -> statement1
expression2 -> statement2
expression3 -> statement3
else -> statement4
}