public void setAppend(boolean flag) {
    fileAppend = flag;
  }
The <b>Append</b> option takes a boolean value. It is set to <code>true</code> by default. If
true, then <code>File</code> will be opened in append mode by {@link #setFile setFile} (see
above). Otherwise, {@link #setFile setFile} will open <code>File</code> in truncate mode.
<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