kotlin, how dynamically change the for loop pace

Question

sometime based on some condition it may want to jump (or move forward) a few steps inside the for loop,

how to do it is kolin?

a simplified use case:

val datArray  = arrayOf(1, 2, 3......)

/**
 * start from the index to process some data, return how many data has been 
   consumed
*/
fun processData_1(startIndex: Int) : Int  {
   // process dataArray starting from the index of startIndex
   // return the data it has processed
}
fun processData_2(startIndex: Int) : Int  {
   // process dataArray starting from the index of startIndex
   // return the data it has processed
}

in Java it could be:

for (int i=0; i<datArray.lenght-1; i++) {
   int processed = processData_1(i);
   i += processed; // jump a few steps for those have been processed, then start 2nd process
   if (i<datArray.lenght-1) { 
       processed = processData_2(i);
       i += processed;
   }
}

How to do it in kotlin?

for(i in array.indices){
  val processed = processData(i);
  // todo
}

I don't think it's a clean solution to change the counter variable manually, use while instead — s1m0nw1
– s1m0nw1, Commented Jun 4, 2018 at 15:10

s1m0nw1 · Accepted Answer · 2018-06-04 15:11:50Z

6

With while:

var i = 0

while (i < datArray.length - 1) {
    var processed = processData_1(i)
    i += processed // jump a few steps for those have been processed, then start 2nd process
    if (i < datArray.length - 1) {
        processed = processData_2(i)
        i += processed
    }
    i++
}

answered Jun 4, 2018 at 15:11

s1m0nw1

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1 Comment

Nikunj Paradva Over a year ago

use datArray.length insted of datArray.length - 1. Because this is lessThan only not lessThan and equalTo

gtRfnkN · Accepted Answer · 2018-06-04 15:17:50Z

0

You can do that with continue as stated in the Kotlin docs here: https://kotlinlang.org/docs/reference/returns.html

Example:

val names = arrayOf("james", "john", "jim", "jacob", "johan")
for (name in names) {
    if(name.length <= 4) continue
    println(name)
}

This would only print names longer than 4 characters (as it skips names with a length of 4 and below)

Edit: this only skips one iteration at a time. So if you want to skip multiple, you could store the process state somewhere else and check the status for each iteration.

answered Jun 4, 2018 at 15:17

gtRfnkN

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