19.thumbHeight=（int）（thumbWidth/imageRatio）;
20.}else{
21.thumbWidth=（int）（thumbHeight*imageRatio）;
22.}
23.
24.//draworiginalimagetothumbnailimageobjectand
25.//scaleittothenewsizeon-the-fly
26.BufferedImagethumbImage=newBufferedImage（thumbWidth,
27.
28.thumbHeight,BufferedImage.TYPE_INT_RGB）;
29.Graphics2Dgraphics2D=thumbImage.createGraphics（）;
30.graphics2D.setRenderingHint（RenderingHints.KEY_INTERPOLATION,
31.
32.RenderingHints.VALUE_INTERPOLATION_BILINEAR）;
33.graphics2D.drawImage（image,0,0,thumbWidth,thumbHeight,null）;
34.
35.//savethumbnailimagetooutFilename
36.BufferedOutputStreamout=newBufferedOutputStream（new
37.
38.FileOutputStream（outFilename））;
39.JPEGImageEncoderencoder=JPEGCodec.createJPEGEncoder（out）;
40.JPEGEncodeParamparam=encoder.getDefaultJPEGEncodeParam
41.
42.（thumbImage）;
43.quality=Math.max（0,Math.min（quality,100））;
44.param.setQuality（（float）quality/100.0f,false）;
45.encoder.setJPEGEncodeParam（param）;
46.encoder.encode（thumbImage）;
47.out.close（）;
48.}
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9.在Java中创建JSON数据
1.Readthisarticleformoredetails.
2.DownloadJARfilejson
3.-rpc-1.0.jar（75kb）
4.importorg.json.JSONObject;
5....
6....
7.JSONObjectjson=newJSONObject（）;
8.json.put（"city","Mumbai"）;
9.json.put（"country","India"）;
10....
11.Stringoutput=json.toString（）;
12....
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10.在Java中使用iTextJAR打开PDF
1.Readthisarticleformoredetails.
2.
3.importjava.io.File;
4.importjava.io.FileOutputStream;
5.importjava.io.OutputStream;
6.importjava.util.Date;
7.
8.importcom.lowagie.text.Document;
9.importcom.lowagie.text.Paragraph;
10.importcom.lowagie.text.pdf.PdfWriter;
11.
12.publicclassGeneratePDF{
13.
14.publicstaticvoidmain（String[]args）{
15.try{
16.OutputStreamfile=newFileOutputStream（newFile（"C:
\\Test.pdf"））;
17.
18.Documentdocument=newDocument（）;
19.PdfWriter.getInstance（document,file）;
20.document.open（）;
21.document.add（newParagraph（"HelloKiran"））;
22.document.add（newParagraph（newDate（）.toString（）））;
23.
24.document.close（）;
25.file.close（）;
26.
27.}catch（Exceptione）{
28.
29.e.printStackTrace（）;
30.}
31.}
32.}
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11.在Java上的HTTP代理设置
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"）;
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12.JavaSingleton例子
1.Readthisarticleformore
2.details.
3.Update:
ThanksMarkusforthecomment.Ihaveupdatedthecodeand
4.changeditto
5.morerobustimplementation.
6.
7.
8.publicclassSimpleSingleton{
9.privatestaticSimpleSingletonsingleInstance= newSimpleSingleton（）;
10.
11.//Markingdefaultconstructorprivate
12.//toavoiddirectinstantiation.
13.privateSimpleSingleton（）{
14.}
15.
16.//GetinstanceforclassSimpleSingleton
17.publicstaticSimpleSingletongetInstance（）{
18.
19.returnsingleInstance;
20.}
21.}
22.OnemoreimplementationofSingletonclass.ThankstoRalphandLukaszZielinski
23.
24.forpointingthisout.
25.
26.
27.publicenumSimpleSingleton{
28.INSTANCE;
29.publicvoiddoSomething（）{
30.}
31.}
32.
33.//CallthemethodfromSingleton:
34.SimpleSingleton.INSTANCE.doSomething（）;
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13.在Java上做屏幕截图
1.Readthisarticleformoredetails.
2.
3.
4.importjava.awt.Dimension;
5.importjava.awt.Rectangle;
6.importjava.awt.Robot;
7.importjava.awt.Toolkit;
8.importjava.awt.image.BufferedImage;
9.importjavax.imageio.ImageIO;
10.importjava.io.File;
11.
12....
13.
14.publicvoidcaptureScreen（StringfileName）throwsException{
15.
16.DimensionscreenSize=Toolkit.getDefaultToolkit（）.getScreenSize（）;
17.RectanglescreenRectangle=newRectangle（screenSize）;
18.Robotrobot=newRobot（）;
19.BufferedImageimage=robot.createScreenCapture（screenRectangle）;
20.ImageIO.write（image,"png",newFile（fileName））;
21.
22.}
23....
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14.在Java中的文件，目录列表
1.Filedir=newFile（"directoryName"）;
2.String[]children=dir.list（）;
3.if（children==null）{
4.//Eitherdirdoesnotexistorisnotadirectory
5.}else{
6.for（inti=0;i7.//Getfilenameoffileordirectory
8.Stringfilename=children;
9.}
10.}
11.
12.//Itisalsopossibletofilterthelistofreturnedfiles.
13.//Thisexampledoesnotreturnanyfilesthatstartwith`.'.
14.FilenameFilterfilter=newFilenameFilter（）{
15.publicbooleanaccept（Filedir,Stringname）{
16.return!
name.startsWith（"."）;
17.}
18.};
19.children=dir.list（filter）;
20.
21.//ThelistoffilescanalsoberetrievedasFileobjects
22.File[]files=dir.listFiles（）;
23.
24.//Thisfilteronlyreturnsdirectories
25.FileFilterfileFilter=newFileFilter（）{
26.publicbooleanaccept（Filefile）{
27.returnfile.isDirectory（）;
28.}
29.};
30.files=dir.listFiles（fileFilter）;
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15.在Java中创建ZIP和JAR文件
1.importjava.util.zip.*;
2.importjava.io.*;
3.
4.publicclassZipIt{
5.publicstaticvoidmain（Stringargs[]）throwsIOException{
6.if（args.length<2）{
7.System.err.println（"usage:
javaZipItZip.zipfile1file2file3"）;
8.System.exit（-1）;
9.}
10.FilezipFile=newFile（args[0]）;
11.if（zipFile.exists（））{
12.System.err.println（"Zipfilealreadyexists,pleasetryanother"）;
13.System.exit（-2）;
14.}
15.FileOutputStreamfos=newFileOutputStream（zipFile）;
16.ZipOutputStreamzos=newZipOutputStream（fos）;
17.intbytesRead;
18.byte[]buffer=newbyte[1024];
19.CRC32crc=newCRC32（）;
20.for（inti=1,n=args.length;i21.Stringname=args;
22.
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