原始碼：
DOM4j.java

package com.zc.homeWork19;

import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

import com.zc.homeWork19.Book;

public
 
 class DOM4j {
    public static void main(String args[]) throws Exception {
        /**
         * 第一步，得到document物件。
         */
        Document document = getDocument();

        /**
         * 第二步，修改得到的document物件
         */

        /**
         * 首先，讀取功能
         */
        List<Book> books = readAllElementsFromXMLDocument(document);
        traverseBooks(books);

        /**
         * 其次，修改功能 修改內容：將id為b002的元素的title改為Java Core，Price改為100.01
         */
 

        ModifyInformationOfXMLDocument(document);

         /**
         * 再者：實現刪除功能 刪除內容：刪除掉id為book1的元素內容。
         */
         deleteInformationOfXMLDocument(document);

         /**
         * 最後：實現新增i新元素功能 新增內容：id為book3，title內容為：鳳姐玉照，price內容為10000.00
         */
         addNewBookToXMLDocument(document);

         /**
         * 第三步：將得到的document物件持久化儲存到硬碟（XML）
         */
 

         writeToNewXMLDocument(document);
    }

    /**
     * 實現了新增新節點：book的功能
     * 
     * @param document
     */
    private static void addNewBookToXMLDocument(Document document) {
        Element root = document.getRootElement();
        Element newBook = root.addElement("book");
        newBook.addAttribute("id", "book3");
        Element title = newBook.addElement("title");
        title.setText("鳳姐玉照");
        Element price = newBook.addElement("price");
        price.setText("10000.01");
    }

    /**
     * 該方法實現了使用dom4j的刪除元素的功能
     * 
     * @param document
     */
    private static void deleteInformationOfXMLDocument(Document document) {
        Element root = document.getRootElement();
        for (Iterator it = root.elementIterator(); it.hasNext();) {
            Element book = (Element) it.next();
            String id = book.attributeValue("id");
            if ("book1".equals(id)) {
                Element parent = book.getParent();
                parent.remove(book);
            }
        }
    }

    /**
     * 該方法的作用是修改document中的內容 將id為b002的元素的title改為Java Core，Price改為100.01
     * 
     * @param document
     */
    private static void ModifyInformationOfXMLDocument(Document document) {
        Element root = document.getRootElement();
        List books = root.elements();
        for (int i = 0; i < books.size(); i++) {

            Element book = (Element) books.get(i);
            if ("book2".equals(book.attributeValue("id"))) {

                for (Iterator it = book.elementIterator(); it.hasNext();) {
                    Element node = (Element) it.next();
                    String type = node.getName();
                    if ("title".equals(type)) {
                        node.setText("JAVA Core");
                    }
                    if ("price".equals(type)) {
                        node.setText("100.01");
                    }
                }
            }
        }

        try {
            writeToNewXMLDocument(document);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    /**
     * 遍歷集合
     * 
     * @param books
     */
    private static void traverseBooks(List<Book> books) {
        for (Iterator<Book> iterator = books.iterator(); iterator.hasNext();) {
            Book book = iterator.next();
            System.out.println(book);
        }
    }

    /**
     * 該方法實現了對xml文件的讀取功能
     * 
     * @param document
     * @return
     */
    private static List<Book> readAllElementsFromXMLDocument(Document document) {
        List<Book> books = new ArrayList<Book>();
        Element root = document.getRootElement();
        List list = root.elements();
        for (int i = 0; i < list.size(); i++) {
            Element book = (Element) list.get(i);
            Book b = new Book();
            String id = book.attributeValue("id");
            List ll = book.elements();
            b.setId(id);
            System.out.println(id);
            for (int j = 0; j < ll.size(); j++) {
                Element element = (Element) ll.get(j);
                if ("title".equals(element.getName())) {
                    String title = element.getText();
                    b.setTitle(title);
                    System.out.println(title);
                }
                if ("price".equals(element.getName())) {
                    String price = element.getText();
                    double p = Double.parseDouble(price);
                    b.setPrice(p);
                    System.out.println(price);
                }
            }
            books.add(b);
        }
        return books;
    }

    /**
     * 通過document物件將記憶體中的dom樹儲存到新的xml文件。
     * 
     * @param document
     * @throws Exception
     */
    private static void writeToNewXMLDocument(Document document)
            throws Exception {

        XMLWriter writer = new XMLWriter(new FileWriter(
                "src/com/zc/homeWork19/newbooks.xml"));
        writer.write(document);
        writer.close();
    }

    /**
     * 該方法用於得到document物件。
     * 
     * @return
     * @throws Exception
     */
    private static Document getDocument() throws Exception {
        SAXReader sr = new SAXReader();
        Document document = sr.read("src\\books.xml");
        return document;
    }
}

Book.java

package com.zc.homeWork19;

public class Book {
    public String title;
    public double price;
    public String id;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String toString() {
        return "圖書ISBN為：" + id + "   書名為：" + title + "    價格為：" + price;
    }
}

book.xml

<?xml version="1.0" encoding="UTF-8"?>
<books>
    <book id="book1">
        <title>JAVA程式設計思想</title>
        <price>80.00</price>
    </book>
    <book id="book2">
        <title>JAVA 程式設計理論</title>
        <price>100.00</price>
    </book>
</books>