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Android Kotlin for Java Developers Modelling Solitaire Removing Cards

Error in for loop ?

Here we are trying to loop from the tapped index to the last index of the MutableList, simultaneously removing the elements from the List... So, for example...

var integers: MutableList<Int> = arrayListOf(0,1,2,3,4,5,6,7,8,9)
for (i in 5..integers.lastIndex)
{
    integers.removeAt(i)
    System.out.println(integers.toString())
}
LOOP 1-------------------
i = 5
integers = [0,1,2,3,4,6,7,8,9] // "5" at Index 5 removed

LOOP 2-------------------
i = 6
integers = [0,1,2,3,4,6,8,9] // "7" at Index 6 removed

LOOP 3-------------------
i = 7
integers = [0,1,2,3,4,6,8] // "9" at Index 7 removed

LOOP 4-------------------
i = 8
integers = [0,1,2,3,4,6,8] // Index 8 OUT OF BOUNDS

We should rather loop backwards

for (i in integers.lastIndex downTo 5)
{
    integers.removeAt(i)
    System.out.println(integers.toString())
}

Console -------------------
[0, 1, 2, 3, 4, 5, 6, 7, 8]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6]
[0, 1, 2, 3, 4, 5]
[0, 1, 2, 3, 4]
-----------------------------

2 Answers

Ben Deitch
STAFF
Ben Deitch
Treehouse Teacher

Yep, that's correct! In the next two videos we add tests for adding/removing cards and we find/fix that bug :)

Yes! :) Just now watched those videos! I should had wondered. It would had been really weird to have missed such a blunder. Sorry for my impatience!

Anyways, the course content is great! Thanks for the efforts.