20非常有用的Java程序片段(6-10)

6. 把 Java util.Date 轉成 sql.Date

1 2	java.util.Date utilDate = newjava.util.Date();   java.sql.Date sqlDate = newjava.sql.Date(utilDate.getTime());

7. 使用NIO進行快速的文件拷貝

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

publicstaticvoidfileCopy( File in, File out )   throwsIOException   {   FileChannel inChannel = newFileInputStream( in ).getChannel();   FileChannel outChannel = newFileOutputStream( out ).getChannel();   try {   //          inChannel.transferTo(0, inChannel.size(), outChannel);      // original -- apparently has trouble copying large files on Windows   // magic number for Windows, 64Mb - 32Kb)   intmaxCount = (64* 1024* 1024) - (32* 1024);   longsize = inChannel.size();   longposition = 0;   while( position < size )   {   position += inChannel.transferTo( position, maxCount, outChannel );   }   }   finally {   if( inChannel != null)   {   inChannel.close();   }   if( outChannel != null)   {   outChannel.close();   }   }   }

8. 創建圖片的縮略圖

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

privatevoidcreateThumbnail(String filename, intthumbWidth, intthumbHeight, intquality, String outFilename)   throwsInterruptedException, FileNotFoundException, IOException   {   // load image from filename   Image image = Toolkit.getDefaultToolkit().getImage(filename);   MediaTracker mediaTracker = newMediaTracker(newContainer());   mediaTracker.addImage(image, 0);   mediaTracker.waitForID(0);   // use this to test for errors at this point: System.out.println(mediaTracker.isErrorAny());   // determine thumbnail size from WIDTH and HEIGHT   doublethumbRatio = (double)thumbWidth / (double)thumbHeight;   intimageWidth = image.getWidth(null);   intimageHeight = image.getHeight(null);   doubleimageRatio = (double)imageWidth / (double)imageHeight;   if(thumbRatio < imageRatio) {   thumbHeight = (int)(thumbWidth / imageRatio);   } else{   thumbWidth = (int)(thumbHeight * imageRatio);   }   // draw original image to thumbnail image object and   // scale it to the new size on-the-fly   BufferedImage thumbImage = newBufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);   Graphics2D graphics2D = thumbImage.createGraphics();   graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);   graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);   // save thumbnail image to outFilename   BufferedOutputStream out = newBufferedOutputStream(newFileOutputStream(outFilename));   JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);   JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);   quality = Math.max(0, Math.min(quality, 100));   param.setQuality((float)quality / 100.0f, false);   encoder.setJPEGEncodeParam(param);   encoder.encode(thumbImage);   out.close();   }

9. 創建 JSON 格式的數據

請先閱讀這篇文章 瞭解一些細節，
並下面這個JAR 文件：json-rpc-1.0.jar (75 kb)

1 2 3 4 5 6 7 8 9

importorg.json.JSONObject;   ...   ...   JSONObject json = newJSONObject();   json.put("city", "Mumbai");   json.put("country", "India");   ...   String output = json.toString();   ...

10. 使用iText JAR生成PDF

閱讀這篇文章 瞭解更多細節

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

importjava.io.File;   importjava.io.FileOutputStream;   importjava.io.OutputStream;   importjava.util.Date;   importcom.lowagie.text.Document;   importcom.lowagie.text.Paragraph;   importcom.lowagie.text.pdf.PdfWriter;   publicclassGeneratePDF {   publicstaticvoidmain(String[] args) {   try{   OutputStream file = newFileOutputStream(newFile("C:\\Test.pdf"));   Document document = newDocument();   PdfWriter.getInstance(document, file);   document.open();   document.add(newParagraph("Hello Kiran"));   document.add(newParagraph(newDate().toString()));   document.close();   file.close();   } catch(Exception e) {   e.printStackTrace();   }   }   }