Concurrency error when using "setColspan()"

[IgorSPaixao]

According to the link http://dynamicjasper.com/2011/12/27/how-to-create-colspan-headers/

I tried to use it in my project in which the error below is presented

java.util.ConcurrentModificationException
	at java.util.ArrayList$SubList.checkForComodification(ArrayList.java:1239)
	at java.util.ArrayList$SubList.get(ArrayList.java:1043)
	at ar.com.fdvs.dj.domain.entities.DJColSpan.isFirstColum(DJColSpan.java:91)
	at ar.com.fdvs.dj.core.layout.AbstractLayoutManager.generateColspanHeader(AbstractLayoutManager.java:529)
[...]

When debugging the list source is DynamicReportBuilder:1656.

To resolve insertion in a new list

cols = new ArrayList<>(cols);