11. HTTP 代理设置
阅读这篇文章了解更多细节。
1.System.getProperties().put("http.proxyHost", "someProxyURL");
2.System.getProperties().put("http.proxyPort", "someProxyPort");
3.System.getProperties().put("http.proxyUser", "someUserName");
4.System.getProperties().put("http.proxyPassword", "somePassword");
2. 单实例Singleton示例
请先阅读这篇文章了解更多信息
1.publicclass SimpleSingleton {
2.privatestatic SimpleSingleton singleInstance = new SimpleSingleton();
3.
4.//Marking default constructor private
5.//to avoid direct instantiation.
6.private SimpleSingleton() {
7. }
8.
9.//Get instance for class SimpleSingleton
10.publicstatic SimpleSingleton getInstance() {
11.
12.return singleInstance;
13. }
14.}
另一种实现
1.publicenum SimpleSingleton {
2. INSTANCE;
3.publicvoid doSomething() {
4. }
5.}
6.
7.//Call the method from Singleton:
8.SimpleSingleton.INSTANCE.doSomething();
13. 抓屏程序
阅读这篇文章获得更多信息。
1.import java.awt.Dimension;
2.import java.awt.Rectangle;
3.import java.awt.Robot;
4.import java.awt.Toolkit;
5.import java.awt.image.BufferedImage;
6.import javax.imageio.ImageIO;
7.import java.io.File;
8.
9....
10.
11.publicvoid captureScreen(String fileName) throws Exception {
12.
13. Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
14. Rectangle screenRectangle = new Rectangle(screenSize);
15. Robot robot = new Robot();
16. BufferedImage image = robot.createScreenCapture(screenRectangle);
17. ImageIO.write(image, "png", new File(fileName));
18.
19.}
20....
14. 列出文件和目录
1.File dir = new File("directoryName");
2. String[] children = dir.list();
3.if (children == null) {
4.// Either dir does not exist or is not a directory
5. } else {
6.for (int i=0; i < children.length; i++) {
7.// Get filename of file or directory
8. String filename = children[i];
9. }
10. }
11.
12.// It is also possible to filter the list of returned files.
13.// This example does not return any files that start with `.'.
14. FilenameFilter filter = new FilenameFilter() {
15.publicboolean accept(File dir, String name) {
16.return !name.startsWith(".");
17. }
18. };
19. children = dir.list(filter);
20.
21.// The list of files can also be retrieved as File objects
22. File[] files = dir.listFiles();
23.
24.// This filter only returns directories
25. FileFilter fileFilter = new FileFilter() {
26.publicboolean accept(File file) {
27.return file.isDirectory();
28. }
29. };
30. files = dir.listFiles(fileFilter);
15. 创建ZIP和JAR文件
1.import java.util.zip.*;
2.import java.io.*;
3.
4.publicclass ZipIt {
5.publicstaticvoid main(String args[]) throws IOException {
6.if (args.length < 2) {
7. System.err.println("usage: java ZipIt Zip.zip file1 file2 file3");
8. System.exit(-1);
9. }
10. File zipFile = new File(args[0]);
11.if (zipFile.exists()) {
12. System.err.println("Zip file already exists, please try another");
13. System.exit(-2);
14. }
15. FileOutputStream fos = new FileOutputStream(zipFile);
16. ZipOutputStream zos = new ZipOutputStream(fos);
17.int bytesRead;
18.byte[] buffer = newbyte[1024];
19. CRC32 crc = new CRC32();
20.for (int i=1, n=args.length; i < n; i++) {
21. String name = args[i];
22. File file = new File(name);
23.if (!file.exists()) {
24. System.err.println("Skipping: " + name);
25.continue;
26. }
27. BufferedInputStream bis = new BufferedInputStream(
28.new FileInputStream(file));
29. crc.reset();
30.while ((bytesRead = bis.read(buffer)) != -1) {
31. crc.update(buffer, 0, bytesRead);
32. }
33. bis.close();
34.// Reset to beginning of input stream
35. bis = new BufferedInputStream(
36.new FileInputStream(file));
37. ZipEntry entry = new ZipEntry(name);
38. entry.setMethod(ZipEntry.STORED);
39. entry.setCompressedSize(file.length());
40. entry.setSize(file.length());
41. entry.setCrc(crc.getValue());
42. zos.putNextEntry(entry);
43.while ((bytesRead = bis.read(buffer)) != -1) {
44. zos.write(buffer, 0, bytesRead);
45. }
46. bis.close();
47. }
48. zos.close();
49. }
50.}
16. 解析/读取XML 文件
XML文件
1.<?xmlversion="1.0"?>
2.<students>
3.<student>
4.<name>John</name>
5.<grade>B</grade>
6.<age>12</age>
7.</student>
8.<student>
9.<name>Mary</name>
10.<grade>A</grade>
11.<age>11</age>
12.</student>
13.<student>
14.<name>Simon</name>
15.<grade>A</grade>
16.<age>18</age>
17.</student>
18.</students>
Java代码:
1.ackage net.viralpatel.java.xmlparser;
2.
3.import java.io.File;
4.import javax.xml.parsers.DocumentBuilder;
5.import javax.xml.parsers.DocumentBuilderFactory;
6.
7.import org.w3c.dom.Document;
8.import org.w3c.dom.Element;
9.import org.w3c.dom.Node;
10.import org.w3c.dom.NodeList;
11.
12.publicclass XMLParser {
13.
14.publicvoid getAllUserNames(String fileName) {
15.try {
16. DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
17. DocumentBuilder db = dbf.newDocumentBuilder();
18. File file = new File(fileName);
19.if (file.exists()) {
20. Document doc = db.parse(file);
21. Element docEle = doc.getDocumentElement();
22.
23.// Print root element of the document
24. System.out.println("Root element of the document: "
25. + docEle.getNodeName());
26.
27. NodeList studentList = docEle.getElementsByTagName("student");
28.
29.// Print total student elements in document
30. System.out
31. .println("Total students: " + studentList.getLength());
32.
33.if (studentList != null && studentList.getLength() > 0) {
34.for (int i = 0; i < studentList.getLength(); i++) {
35.
36. Node node = studentList.item(i);
37.
38.if (node.getNodeType() == Node.ELEMENT_NODE) {
39.
40. System.out
41. .println("=====================");
42.
43. Element e = (Element) node;
44. NodeList nodeList = e.getElementsByTagName("name");
45. System.out.println("Name: "
46. + nodeList.item(0).getChildNodes().item(0)
47. .getNodeValue());
48.
49. nodeList = e.getElementsByTagName("grade");
50. System.out.println("Grade: "
51. + nodeList.item(0).getChildNodes().item(0)
52. .getNodeValue());
53.
54. nodeList = e.getElementsByTagName("age");
55. System.out.println("Age: "
56. + nodeList.item(0).getChildNodes().item(0)
57. .getNodeValue());
58. }
59. }
60. } else {
61. System.exit(1);
62. }
63. }
64. } catch (Exception e) {
65. System.out.println(e);
66. }
67. }
68.publicstaticvoid main(String[] args) {
69.
70. XMLParser parser = new XMLParser();
71. parser.getAllUserNames("c:\\test.xml");
72. }
73.}