Which of the 2 APIs is simpler to read/write/edit excel sheets ? Do these APIs not support CSV extensions ?

Using JXL for file.xls and file.xlsx, I get an exception like: 

jxl.read.biff.BiffException: Unable to recognize OLE stream
    at jxl.read.biff.CompoundFile.<init>(CompoundFile.java:116)
    at jxl.read.biff.File.<init>(File.java:127)
    at jxl.Workbook.getWorkbook(Workbook.java:268)
    at core.ReadXLSheet.contentReading(ReadXLSheet.java:46)
    at core.ReadXLSheet.init(ReadXLSheet.java:22)
    at core.ReadXLSheet.main(ReadXLSheet.java:72)

Both for .xls and .xlsx extensions. Java Version I am using is : JDK1.6

java excel apache-poi jxl
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