如何使用java读取xml，csv？如何标记等？麦克斯韦[关闭]

lndjwyie  于 2023-11-15  发布在  Java
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如何在java中使用BufferedReader读取csv文件。行表示每一行，br.readLine（）表示读取每一行或跳过第一行。当有一行时，我们只需读取每一行，每个值用“;"分隔，我们可以得到一个数组列表来包含每行中的每个值。然后我们使用一个person类来包含这些值。

Java

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按热度按时间
wn9m85ua

wn9m85ua1#

树的前序、中序和后序。

  1. public List<Node> preorder() {
  2.    List<Node> list = new ArrayList<>();
  3.    preOrderHelper(this.root, list);
  4.    return list;
  5. }
  7. // In-Order traversal
  8. // Left Subtree . Node . Right Subtree
  9. public List<Node> inorder() {
  10.    List<Node> list = new ArrayList<>();
  11.    inOrderHelper(this.root, list);
  12.    return list;
  13. }
  15. // Post-Order traversal
  16. // Left Subtree . Right Subtree . Node
  17. public List<Node> postorder() {
  18.    List<Node> list = new ArrayList<>();
  19.    postOrderHelper(this.root, list);
  20.    return list;
  21. }
  23. private void preOrderHelper(Node node, List<Node> list) {
  24.    if (node != null && node.key != null) {
  25.       list.add(node);
  26.       preOrderHelper(node.left, list);
  27.       preOrderHelper(node.right, list);
  28.    }
  29. }
  31. private void inOrderHelper(Node node, List<Node> list) {
  32.    if (node != null && node.key != null) {
  33.       inOrderHelper(node.left, list);
  34.       list.add(node);
  35.       inOrderHelper(node.right, list);
  36.    }
  37. }
  39. private void postOrderHelper(Node node, List<Node> list) {
  40.    if (node != null && node.key != null) {
  41.       postOrderHelper(node.left, list);
  42.       postOrderHelper(node.right, list);
  43.       list.add(node);
  44.    }
  45. }

字符集
The steps of reading，loading and inserting XML

  1. public class XMLTable {
  3.    /**
  4.     * Save all records to the XML file
  5.     */
  6.    public void save(String tableName, List<Customer> customers) {
  8.       File f = new File(FileUtil.getTableFileName(tableName));
  10.       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  11.       try {
  12.          // make the xml tree
  13.          // use factory to get the instance of document builder
  14.          DocumentBuilder db = dbf.newDocumentBuilder();
  15.          Document doc = db.newDocument();
  16.          // Root element <customers>
  17.          Element rootElem = doc.createElement(Customer.KEY_ROOT);
  18.          doc.appendChild(rootElem);
  20.          for (Customer customer : customers) {
  21.             Element customerElem = doc.createElement(Customer.KEY_ELEMENT);
  22.             rootElem.appendChild(customerElem);
  24.             // child element <ID> under <customer>
  25.             Element cid = doc.createElement(Customer.KEY_ID);
  26.             cid.appendChild(doc.createTextNode(Integer.toString(customer.getId())));
  27.             customerElem.appendChild(cid);
  29.             if (customer.getName() != null) {
  30.                Element name = doc.createElement(Customer.KEY_NAME);
  31.                name.appendChild(doc.createTextNode(customer.getName()));
  32.                customerElem.appendChild(name);
  33.             }
  35.             if (customer.getAddress() != null) {
  36.                Element address = doc.createElement(Customer.KEY_ADDRESS);
  37.                address.appendChild(doc.createTextNode(customer.getAddress()));
  38.                customerElem.appendChild(address);
  39.             }
  41.             if (customer.getCity() != null) {
  42.                Element city = doc.createElement(Customer.KEY_CITY);
  43.                city.appendChild(doc.createTextNode(customer.getCity()));
  44.                customerElem.appendChild(city);
  45.             }
  47.             if (customer.getPostCode() != null) {
  48.                Element postCode = doc.createElement(Customer.KEY_POSTCODE);
  49.                postCode.appendChild(doc.createTextNode(customer.getPostCode()));
  50.                customerElem.appendChild(postCode);
  51.             }
  53.             if (customer.getCountry() != null) {
  54.                Element country = doc.createElement(Customer.KEY_COUNTRY);
  55.                country.appendChild(doc.createTextNode(customer.getCountry()));
  56.                customerElem.appendChild(country);
  57.             }
  58.          }
  59.          // save the xml file
  60.          // Transformer is for process XML from a variety of sources and write the
  61.          // transformation
  62.          // output to a variety of sinks
  63.          Transformer transformer = TransformerFactory.newInstance().newTransformer();
  65.          // set xml encoding to utf-8
  66.          transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");
  67.          // pretty print
  68.          transformer.setOutputProperty(OutputKeys.INDENT, "yes");
  70.          DOMSource source = new DOMSource(doc);
  71.          StreamResult result = new StreamResult(f);
  72.          transformer.transform(source, result);
  74.       } catch (Exception e) {
  75.          e.printStackTrace();
  76.       }
  77.    }
  79.    /**
  80.     * Get all records from the XML file
  81.     */
  82.    public List<Customer> load(String tableName) {
  84.       List<Customer> customers = new ArrayList<>();
  86.       File f = new File(FileUtil.getTableFileName(tableName));
  87.       if (!f.exists()) {
  88.          return customers;
  89.       }
  91.       // TODO: Complete this method
  92.       // START YOUR CODE
  93.       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  94.       try {
  95.          // Parse the XML file
  96.          DocumentBuilder db = dbf.newDocumentBuilder();
  97.          Document doc = db.parse(f);
  98.          doc.getDocumentElement().normalize(); // Optional, but recommended
  100.          // Get a NodeList of <customer> elements
  101.          NodeList nodeList = doc.getElementsByTagName(Customer.KEY_ELEMENT);
  103.          for (int i = 0; i < nodeList.getLength(); i++) {
  104.             Node node = nodeList.item(i);
  106.             if (node.getNodeType() == Node.ELEMENT_NODE) {
  107.                Element elem = (Element) node;
  108.                Customer customer = new Customer();
  110.                // Assuming the ID is always present and is an integer
  111.                customer.setId(Integer.parseInt(elem.getElementsByTagName(Customer.KEY_ID).item(0).getTextContent()));
  113.                // Check and set Name if it is present
  114.                if (elem.getElementsByTagName(Customer.KEY_NAME).getLength() > 0) {
  115.                   customer.setName(elem.getElementsByTagName(Customer.KEY_NAME).item(0).getTextContent());
  116.                }
  118.                // Check and set Address if it is present
  119.                if (elem.getElementsByTagName(Customer.KEY_ADDRESS).getLength() > 0) {
  120.                   customer.setAddress(elem.getElementsByTagName(Customer.KEY_ADDRESS).item(0).getTextContent());
  121.                }
  123.                // Check and set City if it is present
  124.                if (elem.getElementsByTagName(Customer.KEY_CITY).getLength() > 0) {
  125.                   customer.setCity(elem.getElementsByTagName(Customer.KEY_CITY).item(0).getTextContent());
  126.                }
  128.                // Check and set Postcode if it is present
  129.                if (elem.getElementsByTagName(Customer.KEY_POSTCODE).getLength() > 0) {
  130.                   customer.setPostCode(elem.getElementsByTagName(Customer.KEY_POSTCODE).item(0).getTextContent());
  131.                }
  133.                // Check and set Country if it is present
  134.                if (elem.getElementsByTagName(Customer.KEY_COUNTRY).getLength() > 0) {
  135.                   customer.setCountry(elem.getElementsByTagName(Customer.KEY_COUNTRY).item(0).getTextContent());
  136.                }
  138.                // Add the customer to the list
  139.                customers.add(customer);
  140.             }
  141.          }
  142.       } catch (Exception e) {
  143.          e.printStackTrace();
  144.       }
  146.       // END YOUR CODE
  148.       return customers;
  149.    }
  151.    /**
  152.     * Insert a new customer to XML files.
  153.     *
  154.     *
  155.     */
  156.    public void insert(String tableName, Customer customer) {
  158.       // TODO: Complete this method
  159.       // START YOU CODE
  160.       // HINT: insert the given customer to the XML file.
  161.       // You can call the load() and save() methods
  162.       List<Customer> customers = load(tableName);
  163.       customers.add(customer);
  164.       save(tableName, customers);
  166.       // END YOUR CODE
  167.    }
  168. }

型
The following steps are used：

  1. public List<Person> readCsv(String fileName) {
  3.    List<Person> list = new LinkedList<>();
  5.    // ########## YOUR CODE STARTS HERE ##########
  6.    String line;
  8.    try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
  9.       br.readLine(); // skip the first line
  11.       while ((line = br.readLine()) != null) {
  12.          Person person = new Person(null,null,null,null);
  14.          String[] values = line.split(";");
  16.          for (int i = 0;i< values.length;i++) {
  17.                switch (i){
  18.                   case 0->{person.setId(Integer.parseInt(values[i]));}
  19.                   case 1->{person.setName(values[i]);}
  20.                   case 2->{person.setAge(Integer.parseInt(values[i]));}
  21.                   case 3->{person.setOccupation(values[i]);}
  22.             }
  23.          }
  24.          list.add(person);
  25.       }
  27.    } catch (IOException e) {
  28.       e.printStackTrace();
  29.    }

型
tokeniser

  1. public void next() {
  3.     buffer = buffer.trim(); // remove whitespace
  5.      if(buffer.isEmpty()) {
  6.         currentToken = null;   // if there's no string left, set currentToken null and return
  7.         return;
  8.      }
  10.     // ########## YOUR CODE STARTS HERE ##########
  11.     StringBuilder token = new StringBuilder();
  12.      for (int i = 0;i<buffer.length();i++){
  13.          char currentChar = buffer.charAt(i);
  14.          if (Character.isDigit(currentChar) || Character.isLetter(currentChar)){
  15.              token.append(currentChar);
  16.          }else if (Character.isWhitespace(currentChar)){
  17.              break;
  18.          }else if(currentChar == '.'){
  19.              if (token.isEmpty()){
  20.                  token.append(".");
  21.                  break;
  22.              }else {
  23.                  break;
  24.              }
  25.          }else {
  26.              token.append(currentChar);
  27.              break;
  28.          }
  29.      }
  31.      String tokenString = token.toString();
  32.      if (isWord(tokenString)){
  33.          if (tokenString.equals(tokenString.toLowerCase())){
  34.              currentToken = new Token(tokenString, Token.Type.LOWER_CASE_WORD);
  35.          }else if (tokenString.equals(tokenString.toUpperCase())) {
  36.              currentToken = new Token(tokenString, Token.Type.UPPER_CASE_WORD);
  37.          }else {
  38.              if (tokenString.length()<=3){
  39.                  currentToken = new Token(tokenString,Token.Type.SHORT_CAMEL_CASE_WORD);
  40.              }else {
  41.                  currentToken = new Token(tokenString,Token.Type.LONG_CAMEL_CASE_WORD);
  42.              }
  43.          }
  44.      }else if (isDigit(tokenString)){
  45.          currentToken = new Token(tokenString, Token.Type.INTEGER_NUMBER);
  46.      }else {
  47.          currentToken = new Token(tokenString,Token.Type.NON_ALPHANUMERIC);
  48.      }
  49.     // ########## YOUR CODE ENDS HERE ##########
  50.     
  51.     // Remove the extracted token from buffer
  52.     int tokenLen = currentToken.getValue().length();
  53.     buffer = buffer.substring(tokenLen);
  54. }

型
parser的步骤

  1. public void parseExp() {
  3.    // TODO: Complete this method
  4.    // START YOUR CODE
  5.    Customer customer = new Customer();
  6.    String attributesString;
  7.    String[] attributesArray = new String[0];
  8.    String[] values = new String[0];
  10.    try{
  11.       for(int i = 0;i<2;i++){
  12.          if (i == 0){
  13.             Token currentToken = tokeniser.takeNext();
  14.             String value = currentToken.value;
  16.             int position_left = 0;
  18.             for (int j = 0;j<value.length()-1;j++){
  19.                if (value.charAt(j) == '('){
  20.                   position_left = j;
  21.                }
  22.             }
  24.             attributesString = value.substring(position_left+1,value.length()-1);
  25.             attributesArray = attributesString.split(",");
  26.          }
  28.          if (i == 1){
  29.             Token currentToken = tokeniser.takeNext();
  30.             String value = currentToken.value;
  32.             value = value.substring(1,value.length()-1);
  34.             values = value.split(", ");
  35.             for (int n=0;n< values.length;n++){
  36.                if (n !=0){
  37.                   values[n] = values[n].substring(1,values[n].length()-1);
  38.                }
  39.             }
  41.          }
  42.       }
  44.       for (int m = 0;m< values.length;m++){
  45.          setCustomerProperty(customer,attributesArray[m],values[m]);
  46.       }
  47.       table.insert(Customer.TABLE_NAME,customer);
  49.    }catch (Exception e){
  51.    }
  53.    // END YOUR CODE
  54. }

型

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