java的常用 java的常用方法

1：//获取当前方法的名称

String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();

2：字符串和整形数据之间 的想换转换

     String a = String.valueOf(2);  
     int i = Integer.parseInt(a);
3：文件末尾添加数据内容

BufferedWriter out = null ;
try {
   out = new BufferedWriter( new FileWriter(”filename”, true ));
   out.write(”aString”);
} catch (IOException e) {
   // error processing code
} finally {
   if (out != null ) {
     out.close();
   }
}
4：使用NIO快速拷贝文件
public static void fileCopy( File in, File out )
       throws IOException
   {
     FileChannel inChannel = new FileInputStream( in ).getChannel();
     FileChannel outChannel = new FileOutputStream( out ).getChannel();
     try
     {
    // inChannel.transferTo(0, inChannel.size(), outChannel);   // original -- apparently has trouble copying large files on Windows
   
       // magic number for Windows, 64Mb - 32Kb)
       int maxCount = ( 64 * 1024 * 1024 ) - ( 32 * 1024 );
       long size = inChannel.size();
       long position = 0 ;
       while ( position < size )
       {
         position += inChannel.transferTo( position, maxCount, outChannel );
       }
     }
     finally
     {
       if ( inChannel != null )
       {
         inChannel.close();
       }
       if ( outChannel != null )
       {
         outChannel.close();
       }
     }
   }
5：创建图片缩略图
private void createThumbnail(String filename, int thumbWidth, int thumbHeight, int quality, String outFilename)
     throws InterruptedException, FileNotFoundException, IOException
   {
     // load image from filename
     Image image = Toolkit.getDefaultToolkit().getImage(filename);
     MediaTracker mediaTracker = new MediaTracker( new Container());
     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
     double thumbRatio = ( double )thumbWidth / ( double )thumbHeight;
     int imageWidth = image.getWidth( null );
     int imageHeight = image.getHeight( null );
     double imageRatio = ( 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 = new BufferedImage(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 = new BufferedOutputStream( new FileOutputStream(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();
   }