11. HTTP 代理設置
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1 2 3 4 5 | System.getProperties().put("http.proxyHost", "someProxyURL"); System.getProperties().put("http.proxyPort", "someProxyPort"); System.getProperties().put("http.proxyUser", "someUserName"); System.getProperties().put("http.proxyPassword", "somePassword"); |
12. 單實例Singleton 示例
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | publicclassSimpleSingleton { privatestaticSimpleSingleton singleInstance = newSimpleSingleton(); //Marking default constructor private //to avoid direct instantiation. privateSimpleSingleton() { } //Get instance for class SimpleSingleton publicstaticSimpleSingleton getInstance() { returnsingleInstance; } } |
另一種實現
1 2 3 4 5 6 7 8 | publicenumSimpleSingleton { INSTANCE; publicvoiddoSomething() { } } //Call the method from Singleton: SimpleSingleton.INSTANCE.doSomething(); |
13. 抓屏程序
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | importjava.awt.Dimension; importjava.awt.Rectangle; importjava.awt.Robot; importjava.awt.Toolkit; importjava.awt.image.BufferedImage; importjavax.imageio.ImageIO; importjava.io.File; ... publicvoidcaptureScreen(String fileName) throwsException { Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); Rectangle screenRectangle = newRectangle(screenSize); Robot robot = newRobot(); BufferedImage image = robot.createScreenCapture(screenRectangle); ImageIO.write(image, "png", newFile(fileName)); } ... |
14. 列出文件和目錄
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | File dir = newFile("directoryName"); String[] children = dir.list(); if(children == null) { // Either dir does not exist or is not a directory } else{ for(inti=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 = newFilenameFilter() { publicbooleanaccept(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 = newFileFilter() { publicbooleanaccept(File file) { returnfile.isDirectory(); } }; files = dir.listFiles(fileFilter); |
15. 創建ZIP和JAR文件
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | importjava.util.zip.*; importjava.io.*; publicclassZipIt { publicstaticvoidmain(String args[]) throwsIOException { if(args.length < 2) { System.err.println("usage: java ZipIt Zip.zip file1 file2 file3"); System.exit(-1); } File zipFile = newFile(args[0]); if(zipFile.exists()) { System.err.println("Zip file already exists, please try another"); System.exit(-2); } FileOutputStream fos = newFileOutputStream(zipFile); ZipOutputStream zos = newZipOutputStream(fos); intbytesRead; byte[] buffer = newbyte[1024]; CRC32 crc = newCRC32(); for(inti=1, n=args.length; i < n; i++) { String name = args[i]; File file = newFile(name); if(!file.exists()) { System.err.println("Skipping: "+ name); continue; } BufferedInputStream bis = newBufferedInputStream( newFileInputStream(file)); crc.reset(); while((bytesRead = bis.read(buffer)) != -1) { crc.update(buffer, 0, bytesRead); } bis.close(); // Reset to beginning of input stream bis = newBufferedInputStream( newFileInputStream(file)); ZipEntry entry = newZipEntry(name); entry.setMethod(ZipEntry.STORED); entry.setCompressedSize(file.length()); entry.setSize(file.length()); entry.setCrc(crc.getValue()); zos.putNextEntry(entry); while((bytesRead = bis.read(buffer)) != -1) { zos.write(buffer, 0, bytesRead); } bis.close(); } zos.close(); } } |