Read And Write Excel With Java - POI Example explains step by step details of reading and writing excel with Apache POI.
Consider an application where you need to manipulate Microsoft office formats, in that case you can use Apache POI
Apache POI project consists of APIs that is used for manipulating various Microsoft office formats, this includes pure java libraries for writing and reading files in Microsoft Office formats, such as Excel, Word and PowerPoint presentations.
Apache POI uses event based API's, this will reduce the memory foot print drastically.
You can see the below example, which is demonstrating Reading & Writing Excel With Apache POI