java读取一个XML文件内容。 2.读取一个EXCEL文件内容，修改后将内容重新写入EXCEL中。 3.读取一个WORD文件内容，修改后将内容重新写入EXCEL中。

1. Java读取一个XML文件内容：

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;

public class ReadXMLFile {
 
   public static void main(String argv[]) {
 
      try {
 
         File inputFile = new File("input.xml");
         DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
         DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
         Document doc = dBuilder.parse(inputFile);
         doc.getDocumentElement().normalize();
 
         System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
 
         NodeList nList = doc.getElementsByTagName("student");
 
         System.out.println("----------------------------");
 
         for (int temp = 0; temp < nList.getLength(); temp++) {
 
            Node nNode = nList.item(temp);
 
            System.out.println("\nCurrent Element :" + nNode.getNodeName());
 
            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
 
               Element eElement = (Element) nNode;
 
               System.out.println("Student roll no : " 
                  + eElement.getAttribute("rollno"));
               System.out.println("First Name : " 
                  + eElement
                  .getElementsByTagName("firstname")
                  .item(0)
                  .getTextContent());
               System.out.println("Last Name : " 
                  + eElement
                  .getElementsByTagName("lastname")
                  .item(0)
                  .getTextContent());
               System.out.println("Nick Name : " 
                  + eElement
                  .getElementsByTagName("nickname")
                  .item(0)
                  .getTextContent());
               System.out.println("Marks : " 
                  + eElement
                  .getElementsByTagName("marks")
                  .item(0)
                  .getTextContent());
            }
         }
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

2. Java读取一个Excel文件内容：

import java.io.File;
import java.io.FileInputStream;
import java.util.Iterator;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ReadExcelFile {
    public static void main(String[] args) {
        try {
            FileInputStream excelFile = new FileInputStream(new File("input.xlsx"));
            Workbook workbook = new XSSFWorkbook(excelFile);
            Sheet datatypeSheet = workbook.getSheetAt(0);
            Iterator<Row> iterator = datatypeSheet.iterator();
            while (iterator.hasNext()) {
                Row currentRow = iterator.next();
                Iterator<Cell> cellIterator = currentRow.iterator();
                while (cellIterator.hasNext()) {
                    Cell currentCell = cellIterator.next();
                    if (currentCell.getCellType() == Cell.CELL_TYPE_STRING) {
                        System.out.print(currentCell.getStringCellValue() + "--");
                    } else if (currentCell.getCellType() == Cell.CELL_TYPE_NUMERIC) {
                        System.out.print(currentCell.getNumericCellValue() + "--");
                    }
                }
                System.out.println();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3. Java读取一个Word文件内容：

import java.io.FileInputStream;
import org.apache.poi.xwpf.usermodel.XWPFDocument;
import org.apache.poi.xwpf.usermodel.XWPFParagraph;
import org.apache.poi.xwpf.usermodel.XWPFRun;

public class ReadWordFile {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("input.docx");
            XWPFDocument document = new XWPFDocument(fis);
            for (XWPFParagraph paragraph : document.getParagraphs()) {
                for (XWPFRun run : paragraph.getRuns()) {
                    String text = run.getText(0);
                    System.out.println(text);
                }
            }
            fis.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

修改并重新写入Excel和Word文件的代码可以根据具体需求进行编写。