How to add a condition to a for loop in Kotlin?

Question

I know that in Java, it is possible to do the following:

boolean condition = true;

for(int i=0; i<array.length && condition; i++){

}

If the condition is false, the for loop stops, but, how to do the same in Kotlin?

There are no counter-based for loops in Kotlin. Just use while loop instead. — broot
– broot, Commented Feb 10, 2022 at 21:47
Have you consulted the documentation? kotlinlang.org/docs/control-flow.html, kotlinlang.org/docs/returns.html — dominicoder
– dominicoder, Commented Feb 10, 2022 at 21:51
What is that you need to do? Maybe there's a more idiomatic way to do it. E.g. array.takeWhile { condition }.forEach { } — gpunto
– gpunto, Commented Feb 10, 2022 at 22:38

DHAVAL A. · Accepted Answer · 2022-02-11 06:30:17Z

3

You can also use the below approach for the conditional for loop.

(0..array.length).takeWhile {
    condition
}.forEach {
    // do something with `it (index)`
}

answered Feb 11, 2022 at 6:30

DHAVAL A.

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3 Comments

k314159 Over a year ago

That should be (0..<array.length), otherwise you'll get an IndexOutOfBoundsException for index = array.length. Better still, use array.indices.

Android_Geek Aug 19 at 17:33

It should be array.size rather array.length, correcting as I got confused when referring to this answer. for(i in 0..< array.size){}

bric3 Sep 15 at 13:49

Careful with this one! The condition is executed array.length times before the forEach.

snachmsm · Accepted Answer · 2022-02-10 22:35:31Z

2

there is no such option in Kotlin (availabe constructions in HERE), but you can add additional check and break keyword

for (i in 0..array.length) {
    if (!condition) break; // quit loop without further iteration
    //rest of code

answered Feb 10, 2022 at 22:35

snachmsm

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1 Comment

k314159 Over a year ago

for (i in 0..<array.length)

ice1000 · Accepted Answer · 2022-02-20 19:46:35Z

1

fun checkCondition(){
  val condition=true
  outerloop@for(i in array.indices) {
    if(array[i]!=condition){
      condition=false
      break@outerloop
    }
  }
  return condition
}

edited Feb 20, 2022 at 19:46

ice1000

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answered Feb 13, 2022 at 10:23

Harikrishnan Jayachandran

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