Java常用方法总结

最新推荐文章于 2022-08-09 21:34:55 发布

原创最新推荐文章于 2022-08-09 21:34:55 发布 · 436 阅读

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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();
  }