How can I restart numbering in Word using Apache POI?

Question

The method below adds numbering successfully. However, when I try to add numbering to other sections which are supposed to start from zero, the numbering added in the first list continues on my second list. How do I restart it?

public void numbering(XWPFDocument document) {
    List<XWPFParagraph> list = document.getParagraphs();
    
    CTAbstractNum cTAbstractNum = CTAbstractNum.Factory.newInstance();
    CTLvl cTLvl = cTAbstractNum.addNewLvl();
    cTLvl.addNewNumFmt().setVal(STNumberFormat.DECIMAL);
    cTLvl.addNewLvlText().setVal("1.");
    cTLvl.addNewStart().setVal(BigInteger.valueOf(1));
    
    XWPFAbstractNum abstractNum = new XWPFAbstractNum(cTAbstractNum);
    XWPFNumbering numbering = document.createNumbering();
    BigInteger abstractNumID = numbering.addAbstractNum(abstractNum);
    BigInteger numID = numbering.addNum(abstractNumID);

    for (XWPFParagraph paragraph : list) {
        
        if (paragraph.getText().trim().contains("This is section number one")|| 
                paragraph.getText().trim().contains("This is section number two") ){
            
            System.out.println(paragraph.getText() + " " + list.indexOf(paragraph));
            paragraph.setNumID(numID);
        }
    }
}

Answer 1

In Apache POI numbered list I have described how basic numbering works in Word.

The NumID set to the paragraph determines the numbering used for that paragraph. So if a new numbering starting with 1. is needed, then a new XWPFAbstractNum needs to be added to the XWPFNumbering and a new NumID needs to be created.

Doing this at simplest could be achieved using a method BigInteger getNewDecimalNumberingId(XWPFDocument document, BigInteger abstractNumID) as follows:

 BigInteger getNewDecimalNumberingId(XWPFDocument document, BigInteger abstractNumID) {
  CTAbstractNum cTAbstractNum = CTAbstractNum.Factory.newInstance();
  cTAbstractNum.setAbstractNumId(abstractNumID);

  CTLvl cTLvl = cTAbstractNum.addNewLvl();
  cTLvl.setIlvl(BigInteger.valueOf(0)); // set indent level 0
  cTLvl.addNewNumFmt().setVal(STNumberFormat.DECIMAL);
  cTLvl.addNewLvlText().setVal("%1.");
  cTLvl.addNewStart().setVal(BigInteger.valueOf(1));

  XWPFAbstractNum abstractNum = new XWPFAbstractNum(cTAbstractNum);

  XWPFNumbering numbering = document.createNumbering();

  abstractNumID = numbering.addAbstractNum(abstractNum);

  BigInteger numID = numbering.addNum(abstractNumID);

  return numID;
 }

This gets a new NumID by adding a new XWPFAbstractNum to the XWPFNumbering.

Complete example for how to use:

import java.io.FileOutputStream;

import org.apache.poi.xwpf.usermodel.*;

import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTAbstractNum;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTLvl;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.STNumberFormat;

import java.math.BigInteger;

public class CreateWordNumberings {

 static BigInteger getNewDecimalNumberingId(XWPFDocument document, BigInteger abstractNumID) {
  CTAbstractNum cTAbstractNum = CTAbstractNum.Factory.newInstance();
  cTAbstractNum.setAbstractNumId(abstractNumID);

  CTLvl cTLvl = cTAbstractNum.addNewLvl();
  cTLvl.setIlvl(BigInteger.valueOf(0)); // set indent level 0
  cTLvl.addNewNumFmt().setVal(STNumberFormat.DECIMAL);
  cTLvl.addNewLvlText().setVal("%1.");
  cTLvl.addNewStart().setVal(BigInteger.valueOf(1));

  XWPFAbstractNum abstractNum = new XWPFAbstractNum(cTAbstractNum);

  XWPFNumbering numbering = document.createNumbering();

  abstractNumID = numbering.addAbstractNum(abstractNum);

  BigInteger numID = numbering.addNum(abstractNumID);

  return numID;
 }

 public static void main(String[] args) throws Exception {

  XWPFDocument document = new XWPFDocument();

  XWPFParagraph paragraph = document.createParagraph();
  XWPFRun run = paragraph.createRun();  
  run.setText("The paragraph before first numbering:");

  //get first NumID for first numbering
  BigInteger numID = getNewDecimalNumberingId(document, BigInteger.valueOf(0));

  paragraph = document.createParagraph();
  paragraph.setNumID(numID);
  run = paragraph.createRun();  
  run.setText("This is first section number one");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("Lorem ipsum semit dolor ...");

  paragraph = document.createParagraph();
  paragraph.setNumID(numID);
  run = paragraph.createRun();  
  run.setText("This is first section number two");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("Lorem ipsum semit dolor ...");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("The paragraph before second numbering:");

  //get second NumID for second numbering
  numID = getNewDecimalNumberingId(document, BigInteger.valueOf(1));

  paragraph = document.createParagraph();
  paragraph.setNumID(numID);
  run = paragraph.createRun();  
  run.setText("This is second section number one");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("Lorem ipsum semit dolor ...");

  paragraph = document.createParagraph();
  paragraph.setNumID(numID);
  run = paragraph.createRun();  
  run.setText("This is second section number two");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("Lorem ipsum semit dolor ...");

  paragraph = document.createParagraph();
  paragraph.setNumID(numID);
  run = paragraph.createRun();  
  run.setText("This is second section number three");

  paragraph = document.createParagraph();
  run = paragraph.createRun();  
  run.setText("Lorem ipsum semit dolor ...");

  paragraph = document.createParagraph();

  FileOutputStream out = new FileOutputStream("CreateWordNumberings.docx");
  document.write(out);
  out.close();
  document.close();

 }
}