New to Java

Hi all,
I've recently started exploring the usage of POI/HSSF to just do simple reading of excel .xls files. The code works fine on excel sheets that i have created on my own. But for some reason, i have tried this reader on a more complicated excel file, and it does not seem to be able to create the HSSFWorkBook from the POIFSFileSystem.

POIFSFileSystem fs = new POIFSFileSystem(new FileInputStream (filename));
HSSFWorkbook hssfworkbook = new HSSFWorkbook(fs);

The following is the error msges displayed after running the program with the more complicated excel file.

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java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at org.apache.poi.hssf.record.RecordFactory.createRecord(RecordFactory.java:224)
at org.apache.poi.hssf.record.RecordFactory.createRecords(RecordFactory.java:160)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:163)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:130)
at ReadExcelExample.main(ReadExcelExample.java:24)
Caused by: java.lang.ArrayIndexOutOfBoundsException
at java.lang.System.arraycopy(Native Method)
at org.apache.poi.hssf.record.UnknownRecord.<init>(UnknownRecord.java:62)
at org.apache.poi.hssf.record.SubRecord.createSubRecord(SubRecord.java:57)
at org.apache.poi.hssf.record.ObjRecord.fillFields(ObjRecord.java:99)
at org.apache.poi.hssf.record.Record.fillFields(Record.java:90)
at org.apache.poi.hssf.record.Record.<init>(Record.java:55)
at org.apache.poi.hssf.record.ObjRecord.<init>(ObjRecord.java:61)
... 9 more
org.apache.poi.hssf.record.RecordFormatException: Unable to construct record instance, the following exception occured: null
at org.apache.poi.hssf.record.RecordFactory.createRecord(RecordFactory.java:237)
at org.apache.poi.hssf.record.RecordFactory.createRecords(RecordFactory.java:160)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:163)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:130)
at ReadExcelExample.main(ReadExcelExample.java:24)
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If anyone could help me solve my problem it would be greatly appreciated. if there is anything else i can provide to help you answer my ques pls let me know.... thank you all for you time.

cheers