Loops
In Kotlin, a loop is a control flow statement that allows repeated execution of a block of code for a certain number of times or until a certain condition is met. Kotlin provides several types of loops, including:
- The
for
loop, which iterates over a range of values or elements in a collection. - The
while
loop, which repeatedly executes a block of code as long as a certain condition is true. - The
do
-while
loop, which is similar to thewhile
loop, but guarantees that the block of code will be executed at least once before the condition is checked.
for
Loop
The for
loop is used to iterate over a range of values or an iterable collection.
Syntax
fun main() {
for (item in collection) {
// Code to be executed for each item
}
}
- The
item
is an element within thecollection
. - The
collection
is any container for a group of items such as lists and sets.
Example
Below is an example of a for
loop that prints the numbers 1 through 10:
fun main() {for(i in 1..10){print(i.toString() + " ")}}
The .toString()
method is used to convert i
to a string so that a string operation can be performed on it. This will output:
1 2 3 4 5 6 7 8 9 10
while
Loop
The while
loop is used to execute a block of code repeatedly as long as a certain condition is true.
Syntax
fun main() {
while (condition) {
// Code to be executed while the condition is true
}
}
While the condition
evaluates to true
, the while loop code block will execute.
Example
The example below uses a while
loop to print the numbers 1 through 10:
fun main() {var i = 1while (i <= 10) {print(" " + i)i++}}
The output for the above code will be:
1 2 3 4 5 6 7 8 9 10
do
-while
Loop
A do
-while
loop in Kotlin is similar to a while
loop, but the code within the do
block is executed before the condition is checked.
Syntax
fun main() {
do {
// Code to be executed at least once
} while (condition)
}
Example
In the example below, a variable i
is declared with an initial value of 10. The loop will continue to run while i
is greater than 0. Upon each iteration of the loop, the value of i
is printed and then decremented by 1 until it is no longer greater than 0. Then, the loop will exit and the program will end:
fun main() {var i = 10do {print(" " + i)i--} while (i > 0)}
This will output:
10 9 8 7 6 5 4 3 2 1
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