POI Introduction
the Java API for Microsoft Documents.
POI Components
1、HSSF/XSSF/SXSSF：Java API To Access Microsoft Excel Format Files.
HSSF/XSSF/SXSSF
HSSF is the POI Project's pure Java implementation of the Excel '97(-2007) file format. XSSF is the POI Project's pure Java implementation of the Excel 2007 OOXML (.xlsx) file format.HSSF and XSSF provides ways to read spreadsheets create, modify, read and write XLS spreadsheets.