How can I create a simple docx file with Apache POI?

I'm searching for a simple example code or a complete tutorial how to create a docx file with Apache POI and its underlying openxml4j.

I tried the following code (with a lot of help from the Content Assist, thanks Eclipse!) but the code does not work correctly.

String tmpPathname = aFilename + ".docx";
File tmpFile = new File(tmpPathname);

ZipP开发者_JAVA百科ackage tmpPackage = (ZipPackage) OPCPackage.create(tmpPathname);
PackagePartName tmpFirstPartName = PackagingURIHelper.createPartName("/FirstPart");
PackagePart tmpFirstPart = tmpPackage.createPart(tmpFirstPartName, "ISO-8859-1");

XWPFDocument tmpDocument = new XWPFDocument(tmpPackage); //Exception
XWPFParagraph tmpParagraph = tmpDocument.createParagraph();
XWPFRun tmpRun = tmpParagraph.createRun();
tmpRun.setText("LALALALAALALAAAA");
tmpRun.setFontSize(18);
tmpPackage.save(tmpFile);

The thrown exception is the following:

Exception in thread "main" java.lang.NullPointerException
    at org.apache.poi.POIXMLDocumentPart.read(POIXMLDocumentPart.java:235)
    at org.apache.poi.POIXMLDocument.load(POIXMLDocument.java:196)
    at org.apache.poi.xwpf.usermodel.XWPFDocument.<init>(XWPFDocument.java:94)
    at DocGenerator.makeDocxWithPoi(DocGenerator.java:64)
    at DocGenerator.main(DocGenerator.java:50)

Does anybody can help me with my (really simple) requirements?

Here is how you can create a simple docx file with POI :

XWPFDocument document = new XWPFDocument();
XWPFParagraph tmpParagraph = document.createParagraph();
XWPFRun tmpRun = tmpParagraph.createRun();
tmpRun.setText("LALALALAALALAAAA");
tmpRun.setFontSize(18);
document.write(new FileOutputStream(new File("yourpathhere")));
document.close();

import java.io.File;   
  import java.io.FileOutputStream;   
  import org.apache.poi.xwpf.usermodel.XWPFDocument;   
  import org.apache.poi.xwpf.usermodel.XWPFParagraph;   
  import org.apache.poi.xwpf.usermodel.XWPFRun;   
  public class DocFile {   
    public void newWordDoc(String filename, String fileContent)   
         throws Exception {   
       XWPFDocument document = new XWPFDocument();   
       XWPFParagraph tmpParagraph = document.createParagraph();   
       XWPFRun tmpRun = tmpParagraph.createRun();   
       tmpRun.setText(fileContent);   
       tmpRun.setFontSize(18);   
       FileOutputStream fos = new FileOutputStream(new File("C:\\Users\\amitabh\\Pictures\\pics\\"+filename + ".doc"));   
       document.write(fos);   
       fos.close();   
    }   
    public static void main(String[] args) throws Exception {   
         DocFile app = new DocFile();   
         app.newWordDoc("testfile", "Hi hw r u?");   

    }   
  }