B4J Question ConcurrentModificationException While Clearing Keys from Map

Daestrum said:

B4X:

    For k = xassets.Size-1 To 0 Step -1
        If xassets.GetKeyAt(k).as(String).Contains("-ob-") Then
            xassets.Remove(xassets.GetKeyAt(k))
        End If
    Next

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Daestrum said:

You might need to start at the end of the map keys and work backwards,. Not sure though.

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B4XDev said:

I'm running this bit of code:

remove keys that match a pattern:

Public Sub ClearOBList
    For Each key As String In xassets.Keys 'xassets is just a map
        If key.Contains("-ob-") Then
            xassets.Remove(key)
        End If
    Next
End Sub

and getting this error: java.util.ConcurrentModificationException

I'm guessing it hasn't finished removing the last key before trying to remove the current key...?

Anybody have an idea? Maybe there's a better way to remove these keys?

Click to expand...

Public Sub ClearOBList
    For Each key As String In xassets.Keys 'xassets is just a map
        If key.Contains("-ob-") Then
            xassets.Remove(key)
            Exit ' <---
        End If
    Next
End Sub

B4XDev said:

For Each key As String In xassets.Keys 'xassets is just a map

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walt61 said:

@LucaMs re "Since keys are unique, there can only be one "-ob-", exit the loop when you find it." : yes but there can be an "-ob-1" and an "-ob-2" and an "-ob-wan-kenobi"

This does the trick:

B4X:

Public Sub ClearOBList
    Dim foundKey As Boolean = True
    Do While foundKey
        foundKey = False
        For Each key As String In xassets.Keys 'xassets is just a map
            If key.Contains("-ob-") Then
                xassets.Remove(key)
                foundKey = True
            End If
        Next
    Loop
End Sub

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LucaMs said:

That's a "nice" comment: "xassets is just a map"
If its name was "mapAssets" there would have been no need for that comment

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