我目前正在使用java（neon eclipse）阅读XML文件。我已经成功完成了，但我在这里遇到了两个问题：
1）我尝试删除XML文件和java。好吧，说实话，我只是在Google中引用编码而我不知道， NodeList 做了什么
2）我想根据XML文件中的标记计算平均值。我不知道如何将它们保存为变量，以后可以进行计算。
这是我的XML文件：
<?xml version="1.0" encoding="UTF-8"?>
<studentMarks>
<student id="1001">
<matricNO>S123</matricNO>
<courseCode>CYY502</courseCode>
<mark>84</mark>
</student>
<student id="1001">
<matricNO>S123</matricNO>
<courseCode>CYY503</courseCode>
<mark>72</mark>
</student>
<student id="1001">
<matricNO>S123</matricNO>
<courseCode>CYY501</courseCode>
<mark>90</mark>
</student>
<student id="1001">
<matricNO>S123</matricNO>
<courseCode>CYY506</courseCode>
<mark>87</mark>
</student>
</studentMarks>
这是我的Java编码：
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 fXmlFile = new File("C:/Users/Lenovo/Desktop/marks.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
NodeList nList = doc.getElementsByTagName("student");
System.out.println(" STUDENT MARKS");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Matric Number : " + eElement.getElementsByTagName("matricNO").item(0).getTextContent());
System.out.println("Course Code : " + eElement.getElementsByTagName("courseCode").item(0).getTextContent());
System.out.println("Marks : " + eElement.getElementsByTagName("mark").item(0).getTextContent());
System.out.println("\n"); //to print new empty line
//---------------------------------calculate the average-------------------------------------
//give a variable to the marks :
//calculate the average :
//-------------------------------------------------------------------------------------------
}
}
System.out.println("Average Marks :");
} catch (Exception e) {
e.printStackTrace();
}
}
}
非常感谢你！
答案 0 :(得分：0)
import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class ReadXMLFile {
public static void main(String argv[]) {
try {
File fXmlFile = new File("C:/Users/Lenovo/Desktop/marks.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
NodeList nList = doc.getElementsByTagName("student");
System.out.println(" STUDENT MARKS");
System.out.println("----------------------------");
Map<String, List<Integer>> matricNOToMarkList = new HashMap<>();
Map<String, List<Integer>> courseCodeToMarkList = new HashMap<>();
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
String matricNO = eElement.getElementsByTagName("matricNO").item(0).getTextContent();
String mark = eElement.getElementsByTagName("mark").item(0).getTextContent();
String courseCode = eElement.getElementsByTagName("courseCode").item(0).getTextContent();
System.out.println("Matric Number : " + matricNO);
System.out.println("Course Code : " + courseCode);
System.out.println("Marks : " + mark);
System.out.println("\n"); //to print new empty line
// if average mark of a student is required
List<Integer> markList = matricNOToMarkList.get(matricNO);
if(markList == null)
{
markList = new ArrayList<>();
matricNOToMarkList.put(matricNO, markList);
}
markList.add(Integer.parseInt(mark));
// if average mark of a course is required
List<Integer> markList1 = courseCodeToMarkList.get(courseCode);
if(markList1 == null)
{
markList1 = new ArrayList<>();
courseCodeToMarkList.put(courseCode, markList1);
}
markList1.add(Integer.parseInt(mark));
}
}
for (String matricNo : matricNOToMarkList.keySet())
{
List<Integer> markList = matricNOToMarkList.get(matricNo);
int sum = 0;
for (Integer mark : markList)
{
sum += mark;
}
System.out.println("Average Marks for MatricNo : " + matricNo + " is : " + (sum/markList.size()));
}
for (String courseCode : courseCodeToMarkList.keySet())
{
List<Integer> markList = courseCodeToMarkList.get(courseCode);
int sum = 0;
for (Integer mark : markList)
{
sum += mark;
}
System.out.println("Average Marks for courseCode : " + courseCode + " is : " + (sum/markList.size()));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
我添加了一张地图（matricNOToMarkList）来保存所有标记，而不是找到一名学生。
我添加了另一个地图（courseCodeToMarkList）来保存针对courseCode的所有标记以查找课程的平均值
希望这有帮助
答案 1 :(得分：0)
我根据我想要的输出编辑了一些@anthoon的答案，我想与其他人分享以便使用此代码：）
import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class Average {
public static void main(String argv[]) {
try {
File fXmlFile = new File("C:/Users/Lenovo/Desktop/marks.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
NodeList nList = doc.getElementsByTagName("student");
System.out.println(" STUDENT MARKS");
System.out.println("----------------------------");
Map<String, List<Integer>> matricNOToMarkList = new HashMap<>();
Map<String, List<Integer>> courseCodeToMarkList = new HashMap<>();
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
String matricNO = eElement.getElementsByTagName("matricNO").item(0).getTextContent();
String mark = eElement.getElementsByTagName("mark").item(0).getTextContent();
String courseCode = eElement.getElementsByTagName("courseCode").item(0).getTextContent();
System.out.println("Matric Number : " + matricNO);
System.out.println("Course Code : " + courseCode);
System.out.println("Marks : " + mark);
System.out.println("\n"); //to print new empty line
// if average mark of a student is required
List<Integer> markList = matricNOToMarkList.get(matricNO);
if(markList == null)
{
markList = new ArrayList<>();
matricNOToMarkList.put(matricNO, markList);
}
markList.add(Integer.parseInt(mark));
// if average mark of a course is required
List<Integer> markList1 = courseCodeToMarkList.get(courseCode);
if(markList1 == null)
{
markList1 = new ArrayList<>();
courseCodeToMarkList.put(courseCode, markList1);
}
markList1.add(Integer.parseInt(mark));
}
}
for (String matricNo : matricNOToMarkList.keySet())
{
List<Integer> markList = matricNOToMarkList.get(matricNo);
float sum = 0;
for (Integer mark : markList)
{
sum += mark;
}
System.out.println("Average Marks is : " + (sum/markList.size()));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}