title: Log4j: from where it initializes itself
body: <p>We are bundling Log4j 1.2.15 with our plain Swing application and load our own properties file from the file system at startup:</p>
  
  <pre><code>import org.apache.log4j.*;
  
  ...
  System.setProperty("log4j.defaultInitOverride", "true");
  ...
  File log4jPropertiesFile = ...
  PropertyConfigurator.configure(log4jPropertiesFile.getAbsolutePath());
  ...
  </code></pre>
  
  <p>In logs we are getting from customers the output does not look like we have defined in the properties file and we are sure that not more than a very small minority edited the file themself.</p>
  
  <p>Could it be that Log4j somehow overrides our settings if there is another configuration file somewhere present on the user's machine available? How we can prevent using that?</p>