Apache POI
Java library for reading and writing Microsoft Office file formats, such as Excel, PowerPoint, Word, Visio, Publisher and Outlook. It supports both the older (OLE2) and new (OOXML - Office Open XML) formats.
en-GB/əˈpæt͡ʃɪ ˈpɔɪ/
en-US/əˈpæt͡ʃi pɔɪ/