How to insert value into specific column in csv file using java

Question

I want write multiple xml file data into one csv file, For first time writing data from first xml into csv file 8 columns created and for second xml file data writing into from 9th column of same csv file, How can we insert the data into specific column. list contains xml data.

String[] rowValue = new String[list.size()];
rowValue = list.toArray(rowValue);
writer.writerNext(rowValue,true);