java 获取zip里附加注释

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jdk里面提供了往zip包里添加注释的api方法ZipOutputStream里的setComment,但似乎找不到如何获取zip包里的附加注释的方法,在google里搜了一下,在一个英文网站里发现这个方法,测试可用.

public static String extractZipComment (String filename) {
			String retStr = null;
			try {
			File file = new File(filename);
			int fileLen = (int)file.length();
			 
			FileInputStream in = new FileInputStream(file);
			 
			/* The whole ZIP comment (including the magic byte sequence)
			* MUST fit in the buffer
			* otherwise, the comment will not be recognized correctly
			*
			* You can safely increase the buffer size if you like
			*/
			byte[] buffer = new byte[Math.min(fileLen, 8192)];
			int len;
			 
			in.skip(fileLen - buffer.length);
			 
			if ((len = in.read(buffer)) > 0) {
			retStr = getZipCommentFromBuffer (buffer, len);
			}
			 
			in.close();
			} catch (Exception e) {
			e.printStackTrace();
			}
			return retStr;
	}
		 
	private static String getZipCommentFromBuffer (byte[] buffer, int len) {
			byte[] magicDirEnd = {0x50, 0x4b, 0x05, 0x06};
			int buffLen = Math.min(buffer.length, len);
			//Check the buffer from the end
			for (int i = buffLen-magicDirEnd.length-22; i >= 0; i--) {
				boolean isMagicStart = true;
				for (int k=0; k < magicDirEnd.length; k++) {
					if (buffer[i+k] != magicDirEnd[k]) {
					isMagicStart = false;
					break;
					}
				}
				if (isMagicStart) {
					//Magic Start found!
					int commentLen = buffer[i+20] + buffer[i+22]*256;
					int realLen = buffLen - i - 22;
					System.out.println ("ZIP comment found at buffer position " + (i+22) + " with len="+commentLen+", good!");
					if (commentLen != realLen) {
					System.out.println ("WARNING! ZIP comment size mismatch: directory says len is "+
					commentLen+", but file ends after " + realLen + " bytes!");
					}
					String comment = new String (buffer, i+22, Math.min(commentLen, realLen));
					return comment;
				}
			}
			System.out.println ("ERROR! ZIP comment NOT found!");
			return null;
	}