docs: public static boolean contentEquals(File file1, File file2) throws IORuntimeException {
  		boolean file1Exists = file1.exists();
  		if (file1Exists != file2.exists()) {
  			return false;
  		}
  
  		if (false == file1Exists) {
  			// 两个文件都不存在，返回true
  			return true;
  		}
  
  		if (file1.isDirectory() || file2.isDirectory()) {
  			// 不比较目录
  			throw new IORuntimeException("Can't compare directories, only files");
  		}
  
  		if (file1.length() != file2.length()) {
  			// 文件长度不同
  			return false;
  		}
  
  		if (equals(file1, file2)) {
  			// 同一个文件
  			return true;
  		}
  
  		InputStream input1 = null;
  		InputStream input2 = null;
  		try {
  			input1 = getInputStream(file1);
  			input2 = getInputStream(file2);
  			return IoUtil.contentEquals(input1, input2);
  
  		} finally {
  			IoUtil.close(input1);
  			IoUtil.close(input2);
  		}
  	}