public void setFile(String file) {
    // Trim spaces from both ends. The users probably does not want
    // trailing spaces in file names.
    String val = file.trim();
    fileName = val;
  }
The <b>File</b> property takes a string value which should be the name of the file to append
to.
<p>
<font color="#DD0044"><b>Note that the special values "System.out" or "System.err" are no
longer honored.</b></font>
<p>
Note: Actual opening of the file is made when {@link #activateOptions} is called, not when the
options are set.
hbase-logging/src/test/java/org/apache/log4j/FileAppender.java