关于XML文件的写入数据的疑问

package 从网页搭建入门JavaWeb.步骤三JavaWeb入门.XML入门;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;

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

public class XMLWriter {

	public static void main(String[] args) {
		// String file =
		// "D:/compiling_software/eclipse/eclipse/workspace/慕课网/src/从网页搭建入门JavaWeb/步骤三JavaWeb入门/XML入门/plan.xml";
		String file = "src/从网页搭建入门JavaWeb/步骤三JavaWeb入门/XML入门/plan.xml";
		SAXReader reader = new SAXReader();
		try {
			Document document = reader.read(file);
			Element root = document.getRootElement();
			Element newElement = root.addElement("course");
			Element newElementName = newElement.addElement("course-name");
			newElementName.setText("计算机网络");
			Element newElementHour = newElement.addElement("calss-hour");
			newElementHour.setText("80");
			Element newElementForm = newElement.addElement("exam-form");
			newElementForm.setText("考试");
			newElement.addAttribute("id", "TC004");
			Writer writer = new OutputStreamWriter(new FileOutputStream(file), "GBK");
			document.write(writer);
			System.out.println("写入完毕");
		} catch (DocumentException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		} catch (IOException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
	}

}

package 从网页搭建入门JavaWeb.步骤三JavaWeb入门.XML入门;

import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class XMLreader {

	public static void main(String[] args) {
		// String file = "d:/compiling_software/eclipse/eclipse/workspace/慕课网/src/从网页搭建入门JavaWeb/步骤三JavaWeb入门/XML入门/plan.xml";
		String file = "src/从网页搭建入门JavaWeb/步骤三JavaWeb入门/XML入门/plan.xml";
		SAXReader reader = new SAXReader();
		try {
			Document document = reader.read(file);
			Element root = document.getRootElement();
			List<Element> elements = root.elements("course");
			for (Element ele : elements) {
				Attribute att = ele.attribute("id");
				String id = att.getText();
				Element name = ele.element("course-name");
				String course_name = name.getText();
				Element hour = ele.element("class-hour");
				String class_hour = hour.getText();
				Element form = ele.element("exam-form");
				String exam_form = form.getText();
				System.out.println("课程ID：" + id);
				System.out.println("课程名称：" + course_name);
				System.out.println("课程课时：" + class_hour);
				System.out.println("考核方式：" + exam_form);
			}
		} catch (DocumentException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
	}

}

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema">
	<element name="teaching-plan">
		<complexType>
			<sequence>
				<element name="course" maxOccurs="100">
					<complexType>
						<sequence>
							<element name="course-name" type="string"></element>
							<element name="class-hour">
								<simpleType>
									<restriction base="integer">
										<minInclusive value="20"></minInclusive>
										<maxInclusive value="110"></maxInclusive>
									</restriction>
								</simpleType>
							</element>
							<element name="exam-form" type="string"></element>
						</sequence>
						<attribute name="id" type="string" use="required"></attribute>
					</complexType>
				</element>
			</sequence>
		</complexType>
	</element>
</schema>

<?xml version="1.0" encoding="UTF-8"?>

<teaching-plan xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="plan.xsd">
	<course id="TC001">
		<course-name>高等数学</course-name>
		<class-hour>36</class-hour>
		<exam-form>考试</exam-form>
	</course>
	<course id="TC002">
		<course-name>计算机二级</course-name>
		<class-hour>48</class-hour>
		<exam-form>上机考试</exam-form>
	</course>
	<course id="TC003">
		<course-name>汇编语言</course-name>
		<class-hour>106</class-hour>
		<exam-form>考试</exam-form>
	</course>
</teaching-plan>