```public fun <T> MutableList<T>.remov...

# stdlib

[diego-gomez-olvera]

public fun <T> MutableList<T>.removeAll(predicate: (T) -> Boolean): Boolean = filterInPlace(predicate, true)

private fun <T> MutableList<T>.filterInPlace(predicate: (T) -> Boolean, predicateResultToRemove: Boolean): Boolean {
    if (this !is RandomAccess)
        return (this as MutableIterable<T>).filterInPlace(predicate, predicateResultToRemove)

    var writeIndex: Int = 0
    for (readIndex in 0..lastIndex) {
        val element = this[readIndex]
    ...
        if (writeIndex != readIndex)
            this[writeIndex] = element
     ...
}

It seems CopyOnWriteArrayList.removeAll does not copy on write but mutates in place instead

[gian]

How so? Isn’t CopyOnWriteArrayList::set copying the array before mutation?

[diego-gomez-olvera]

indeed

[diego-gomez-olvera]

I am puzzled but a crash

java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
        at java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:385)
        at java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:398)
        at kotlin.collections.CollectionsKt__MutableCollectionsKt.filterInPlace$CollectionsKt__MutableCollectionsKt(MutableCollections.kt:190)
        at kotlin.collections.CollectionsKt__MutableCollectionsKt.removeAll(MutableCollections.kt:177)

[diego-gomez-olvera]

and lastIndex should be recalculated

[Shivam]

Getting a similar crash while doing removeAll. I'm using SynchronizedList but I don't get why it's throwing IndexOutOfBounds.

java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
	at jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
	at jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
	at java.util.Objects.checkIndex(Objects.java:385)
	at java.util.ArrayList.remove(ArrayList.java:558)
	at java.util.Collections$SynchronizedList.remove(Collections.java:2791)
	at kotlin.collections.CollectionsKt__MutableCollectionsKt.filterInPlace$CollectionsKt__MutableCollectionsKt(CollectionsKt__MutableCollectionsKt.java:296)
	at kotlin.collections.CollectionsKt__MutableCollectionsKt.removeAll(CollectionsKt__MutableCollectionsKt.java:270)