java.util.ConcurrentModificationException when try to remove item from list in android

Question

I have list of variants where every variant has list of colors. I want to check for every variant if has color from filter and if no, I want to remove that variant from list of variants. When I tried to remove I get error: java.util.ConcurrentModificationException This is what I tried:

list.map { variant ->
    variant.variantColors.map { color ->
        if (color != filterModel.color) {
            list.removeIf { color != filterModel.color }
        }
    }
}

and:

list.map { variant ->
    variant.variantColors.map { color ->
        if (color != filterModel.color) {
            list.removeAll { color != filterModel.color }
        }
    }
}

and:

val iterator = list.iterator()
while (iterator.hasNext()) {
    val item = iterator.next()
    val iteratorSec = item.variantColors.iterator()
    while (iteratorSec.hasNext()) {
        val itema = iteratorSec.next()
        if (itema != filterModel.color)
            iterator.remove()
    }
}

Please share the full crash log/stacktrace.

Sufian
– Sufian

2019-04-09 13:13:21 +00:00
Commented Apr 9, 2019 at 13:13 — Sufian
– Sufian, Commented Apr 9, 2019 at 13:13

Sasi Kumar · Accepted Answer · 2019-04-09 13:04:39Z

2

Use list filter function like this for your concept

 fun main()
 {
  val myList : MutableList<ColorInfo> = mutableListOf(
    ColorInfo(color = "red",colorcode = "1111"),
    ColorInfo(color = "green",colorcode = "1123"),
    ColorInfo(color = "yellow",colorcode = "1134")
)


val filteredList = myList.filter { !it.color.equals("red") }
println(filteredList.toString())
 //out put is [Event(color=green, colorcode=1123), Event(color=yellow, colorcode=1134)]
}

data class ColorInfo(var color : String,var colorcode : String)

answered Apr 9, 2019 at 13:04

Sasi Kumar

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Comments

Nikolay · Accepted Answer · 2019-04-09 13:47:22Z

0

It happens because you're trying mutate you list inside map() callback while it's iterating around list. To avoid it you should call removeAll()/removeIf() first:

class Variant(val colors: List<Int>)

fun main() {
    val badColor = 2
    val variants = mutableListOf(
            Variant(listOf(1, 2, 3)),
            Variant(listOf(2, 4, 6)),
            Variant(listOf(3, 5, 7)))
    // try removeAll()
    variants.removeAll {
        it in variants.filter {variant ->
            badColor in variant.colors
        }
    }
    //  or removeIf()
    variants.removeIf {
        badColor in it.colors
    }

    print(variants)
}

answered Apr 9, 2019 at 13:47

Nikolay

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