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How to Read, Write XLSX File in Java - Apach POI Example

No matter how Microsoft is doing in comparison with Google, Microsoft Office is still the most used application in software world. Other alternatives like OpenOffice and LiberOffice have failed to take off to challenge MS Office. What this mean to a Java application developer? Because of huge popularity of MS office products you often need to support Microsoft office format such as word, Excel, PowerPoint and additionally Adobe PDF. If you are using JSP Servlet, display tag library automatically provides Excel, Word and PDF support. Since JDK doesn't provide direct API to read and write Microsoft Excel and Word document, you have to rely on third party library to do your job. Fortunately there are couple of open source library exists to read and write Microsoft Office XLS and XLSX file format, Apache POI is the best one. It is widely used, has strong community support and it is feature rich.

Why Constructor is Important in Java?

In simple word, Constructor is a method like a block of code which is called by Java runtime during object creation using new() operator. Constructor are special in the sense that they have the same name as the Class they are part of. They are also special in a sense that they are called by JVM automatically when you create an object. Have you ever thought about Why do you need a constructor? What benefits it provide? One reason is to initialize your object with default or initial state since default values for primitives may not be what you are looking for. One more reason you create constructor is to inform the world about dependencies, a class needs to do its job. Anyone by looking at your constructors should be able to figure out, what he needs in order to use this class.  For example, following class OrderProcessor needs a Queue and Database to function properly.