code: public String getSourceLine(File file, int line, String sep)
  	{
  		SourceFile source = sourceFiles.get(file);
  
  		if (source == null)
  		{
  			try
  			{
  				source = new SourceFile(file);
  				sourceFiles.put(file, source);
  			} catch (IOException e)
  			{
  				return "Cannot open source file: " + file;
  			}
  		}
  
  		return line + sep + source.getLine(line);
  	}
docs: Get a line of a source file by its location.
  
  @param file
  @param line
  @param sep
  @return