常用Java程式片段

標籤：htm   nod   name   username   default   retrieve   mini   http   reflect   

1、改變數組的大小 

package com.js.ai.modules.jsa.test;public class Testxf {private static Object resizeArray(Object oldArray, int newSize){int oldSize=java.lang.reflect.Array.getLength(oldArray);Class elementType=oldArray.getClass().getComponentType();Object newArray=java.lang.reflect.Array.newInstance(elementType, newSize);int preserveLength=Math.min(oldSize, newSize);if(preserveLength>0)System.arraycopy(oldArray, 0, newArray, 0, preserveLength);return newArray;}public static void main(String[] args) {int[] a = {1,2,3};      a = (int[])resizeArray(a,5);   a[3] = 4;       a[4] = 5;       for (int i=0; i<a.length; i++)          System.out.print (a[i]+";");  }}

　2、發送代資料的HTTP 要求

package com.js.ai.modules.jsa.test;import java.io.BufferedReader;import java.io.InputStreamReader;import java.net.URL;public class Testxf {public static void main(String[] args) {try {URL my_url=new URL("https://open.alipay.com/platform/home.htm");BufferedReader br=new BufferedReader(new InputStreamReader(my_url.openStream())); String strTemp = "";   while(null!=(strTemp=br.readLine())){ System.out.println(strTemp); }} catch (Exception e) {e.printStackTrace();}}}

3、發送郵件 

package com.js.ai.modules.jsa.test;import java.util.Properties;import javax.mail.Message;import javax.mail.MessagingException;import javax.mail.Session;import javax.mail.Transport;import javax.mail.internet.InternetAddress;import javax.mail.internet.MimeMessage;public class Testxf {public void postMail(String recipients[], String subject, String message, String from) throws MessagingException {boolean debug = false;// Set the host smtp addressProperties props = new Properties();props.put("mail.smtp.host", "smtp.example.com");// create some properties and get the default SessionSession session = Session.getDefaultInstance(props, null);session.setDebug(debug);// create a messageMessage msg = new MimeMessage(session);// set the from and to addressInternetAddress addressFrom = new InternetAddress(from);msg.setFrom(addressFrom);InternetAddress[] addressTo = new InternetAddress[recipients.length];for (int i = 0; i < recipients.length; i++) {addressTo[i] = new InternetAddress(recipients[i]);}msg.setRecipients(Message.RecipientType.TO, addressTo);// Optional : You can also set your custom headers in the Email if you// Wantmsg.addHeader("MyHeaderName", "myHeaderValue");// Setting the Subject and Content Typemsg.setSubject(subject);msg.setContent(message, "text/plain");Transport.send(msg);}}

4、把 Array 轉換成 Map 

public static void main(String[] args) {        String[][] countries = { { "United States", "New York" }, { "United Kingdom", "London" },            { "Netherland", "Amsterdam" }, { "Japan", "Tokyo" }, { "France", "Paris" } };          Map countryCapitals = ArrayUtils.toMap(countries);          System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));        System.out.println("Capital of France is " + countryCapitals.get("France"));      }    

5、解析/讀取XML 檔案

XML檔案 ：<?xml version="1.0"?>   <students>       <student>           <name>John</name>           <grade>B</grade>           <age>12</age>       </student>       <student>           <name>Mary</name>           <grade>A</grade>           <age>11</age>       </student>       <student>           <name>Simon</name>           <grade>A</grade>           <age>18</age>       </student>   </students>  java代碼：import java.io.File;    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 XMLParser {          public void getAllUserNames(String fileName) {            try {                DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();                DocumentBuilder db = dbf.newDocumentBuilder();                File file = new File(fileName);                if (file.exists()) {                    Document doc = db.parse(file);                    Element docEle = doc.getDocumentElement();                      // Print root element of the document                    System.out.println("Root element of the document: "                           + docEle.getNodeName());                      NodeList studentList = docEle.getElementsByTagName("student");                      // Print total student elements in document                    System.out                            .println("Total students: " + studentList.getLength());                      if (studentList != null && studentList.getLength() > 0) {                        for (int i = 0; i < studentList.getLength(); i++) {                              Node node = studentList.item(i);                              if (node.getNodeType() == Node.ELEMENT_NODE) {                                  System.out                                        .println("=====================");                                  Element e = (Element) node;                                NodeList nodeList = e.getElementsByTagName("name");                                System.out.println("Name: "                                       + nodeList.item(0).getChildNodes().item(0)                                                .getNodeValue());                                  nodeList = e.getElementsByTagName("grade");                                System.out.println("Grade: "                                       + nodeList.item(0).getChildNodes().item(0)                                                .getNodeValue());                                  nodeList = e.getElementsByTagName("age");                                System.out.println("Age: "                                       + nodeList.item(0).getChildNodes().item(0)                                                .getNodeValue());                            }                        }                    } else {                        System.exit(1);                    }                }            } catch (Exception e) {                System.out.println(e);            }        }        public static void main(String[] args) {              XMLParser parser = new XMLParser();            parser.getAllUserNames("c:\\test.xml");        }    } 

6、列出檔案和目錄

File dir = new File("directoryName");      String[] children = dir.list();      if (children == null) {          // Either dir does not exist or is not a directory      } else {          for (int i=0; i < children.length; i++) {              // Get filename of file or directory              String filename = children[i];          }      }        // It is also possible to filter the list of returned files.      // This example does not return any files that start with `.‘.      FilenameFilter filter = new FilenameFilter() {          public boolean accept(File dir, String name) {              return !name.startsWith(".");          }      };      children = dir.list(filter);        // The list of files can also be retrieved as File objects      File[] files = dir.listFiles();        // This filter only returns directories      FileFilter fileFilter = new FileFilter() {          public boolean accept(File file) {              return file.isDirectory();          }      };      files = dir.listFiles(fileFilter); 

7、抓屏程式 

package com.js.ai.modules.jsa.test;import java.awt.Dimension;import java.awt.Rectangle;import java.awt.Robot;import java.awt.Toolkit;import java.awt.image.BufferedImage;import java.io.File;import javax.imageio.ImageIO;public class Testxf {public void captureScreen(String fileName) throws Exception {         Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();       Rectangle screenRectangle = new Rectangle(screenSize);       Robot robot = new Robot();       BufferedImage image = robot.createScreenCapture(screenRectangle);       ImageIO.write(image, "png", new File(fileName));      } public static void main(String[] args) throws Exception {Testxf testxf =new Testxf();testxf.captureScreen("C:/Users/Administrator/Desktop/JSAxfz/captureScreen.png");}}

　　

常用Java程式片段