POI API Documentation

DDF - Dreadful Drawing Format 
Package Description
org.apache.poi.ddf
This package contains classes for decoding the Microsoft Office Drawing format otherwise known as escher henceforth known in POI as the Dreadful Drawing Format.
HPSF - Horrible Property Set Format 
Package Description
org.apache.poi.hpsf
org.apache.poi.hpsf.extractor  
org.apache.poi.hpsf.wellknown
Specific support for DocumentSummaryInformation, SummaryInformation types.
HSSF - Horrible Spreadsheet Format 
Package Description
org.apache.poi.hssf
Horrible SpreadSheet Format API's for reading/writting Excel files using pure Java.
org.apache.poi.hssf.converter  
org.apache.poi.hssf.dev
DEV package serves two purposes.
org.apache.poi.hssf.eventmodel  
org.apache.poi.hssf.eventusermodel
HSSF eventmodel Package provides an event-based API for reading HSSF files.
org.apache.poi.hssf.eventusermodel.dummyrecord  
org.apache.poi.hssf.extractor  
org.apache.poi.hssf.model
Provides low level API structures for reading, writing, modifying XLS files.
org.apache.poi.hssf.record
Record package contains class representations for XLS binary strutures.
org.apache.poi.hssf.record.aggregates
record aggregates are not real "records" but collections of records that act as a single record.
org.apache.poi.hssf.record.cf  
org.apache.poi.hssf.record.chart  
org.apache.poi.hssf.record.common  
org.apache.poi.hssf.record.cont  
org.apache.poi.hssf.record.crypto  
org.apache.poi.hssf.record.pivottable  
org.apache.poi.hssf.usermodel
usermodel package maps HSSF low level strutures to familiar workbook/sheet model
org.apache.poi.hssf.util
util package contains tools needed for writing HSSF files that are not necesarily "real" HSSF concepts.
HWPF - Horrible Word Processor Format 
Package Description
org.apache.poi.hwpf  
org.apache.poi.hwpf.converter  
org.apache.poi.hwpf.dev  
org.apache.poi.hwpf.extractor  
org.apache.poi.hwpf.model  
org.apache.poi.hwpf.model.io  
org.apache.poi.hwpf.model.types  
org.apache.poi.hwpf.sprm  
org.apache.poi.hwpf.usermodel  
POIFS - POI File System 
Package Description
org.apache.poi.poifs.common
common package contains constants and other classes shared across all POIFS subpackages
org.apache.poi.poifs.crypt
Implementation of the ECMA-376 Document Encryption
org.apache.poi.poifs.crypt.agile  
org.apache.poi.poifs.crypt.standard  
org.apache.poi.poifs.dev
DEV package serves two purposes.
org.apache.poi.poifs.eventfilesystem
The eventfilesystem is an efficient method for reading OLE 2 CDF files.
org.apache.poi.poifs.filesystem
filesystem package maps OLE 2 Compound document files to a more familiar filesystem interface.
org.apache.poi.poifs.nio  
org.apache.poi.poifs.property
property package contains high and low level Property structures for POIFS.
org.apache.poi.poifs.storage
storage package contains low level binary structures for POIFS's implementation of the OLE 2 Compound Document Format.
Utilities 
Package Description
org.apache.poi.util
Top-level util package are classes that are useful throughout the project.
Other Packages 
Package Description
org.apache.poi  
org.apache.poi.common.usermodel  
org.apache.poi.dev  
org.apache.poi.extractor  
org.apache.poi.hdgf  
org.apache.poi.hdgf.chunks  
org.apache.poi.hdgf.dev  
org.apache.poi.hdgf.exceptions  
org.apache.poi.hdgf.extractor  
org.apache.poi.hdgf.pointers  
org.apache.poi.hdgf.streams  
org.apache.poi.hmef  
org.apache.poi.hmef.attribute  
org.apache.poi.hmef.dev  
org.apache.poi.hmef.extractor  
org.apache.poi.hpbf  
org.apache.poi.hpbf.dev  
org.apache.poi.hpbf.extractor  
org.apache.poi.hpbf.model  
org.apache.poi.hpbf.model.qcbits  
org.apache.poi.hslf  
org.apache.poi.hslf.blip  
org.apache.poi.hslf.dev  
org.apache.poi.hslf.exceptions  
org.apache.poi.hslf.extractor  
org.apache.poi.hslf.model  
org.apache.poi.hslf.model.textproperties  
org.apache.poi.hslf.record  
org.apache.poi.hslf.usermodel  
org.apache.poi.hslf.util  
org.apache.poi.hsmf  
org.apache.poi.hsmf.datatypes  
org.apache.poi.hsmf.dev  
org.apache.poi.hsmf.exceptions  
org.apache.poi.hsmf.extractor  
org.apache.poi.hsmf.parsers  
org.apache.poi.openxml4j.exceptions  
org.apache.poi.openxml4j.opc  
org.apache.poi.openxml4j.opc.internal  
org.apache.poi.openxml4j.opc.internal.marshallers  
org.apache.poi.openxml4j.opc.internal.signature  
org.apache.poi.openxml4j.opc.internal.unmarshallers  
org.apache.poi.openxml4j.opc.signature  
org.apache.poi.openxml4j.util  
org.apache.poi.sl.usermodel  
org.apache.poi.ss  
org.apache.poi.ss.extractor  
org.apache.poi.ss.format
This package contains classes that implement cell formatting
org.apache.poi.ss.formula
This package contains common internal POI code for manipulating formulas.
org.apache.poi.ss.formula.atp  
org.apache.poi.ss.formula.constant  
org.apache.poi.ss.formula.eval  
org.apache.poi.ss.formula.eval.forked  
org.apache.poi.ss.formula.function  
org.apache.poi.ss.formula.functions  
org.apache.poi.ss.formula.ptg
formula package contains binary PTG structures used in Formulas
org.apache.poi.ss.formula.udf  
org.apache.poi.ss.usermodel  
org.apache.poi.ss.usermodel.charts  
org.apache.poi.ss.util  
org.apache.poi.ss.util.cellwalk  
org.apache.poi.xslf  
org.apache.poi.xslf.extractor  
org.apache.poi.xslf.model  
org.apache.poi.xslf.model.geom  
org.apache.poi.xslf.usermodel  
org.apache.poi.xslf.util  
org.apache.poi.xssf  
org.apache.poi.xssf.dev  
org.apache.poi.xssf.eventusermodel  
org.apache.poi.xssf.extractor  
org.apache.poi.xssf.model  
org.apache.poi.xssf.streaming  
org.apache.poi.xssf.usermodel  
org.apache.poi.xssf.usermodel.charts  
org.apache.poi.xssf.usermodel.extensions  
org.apache.poi.xssf.usermodel.helpers  
org.apache.poi.xssf.util  
org.apache.poi.xwpf.extractor  
org.apache.poi.xwpf.model  
org.apache.poi.xwpf.usermodel  

Copyright 2014 The Apache Software Foundation or its licensors, as applicable.