question: void initProperties ( String defaultLevel , String defaultFilter , String defaultFormatter , String defaultEncoding ) { LogManager manager = LogManager . getLogManager ( ) ; final String filterName = manager . getProperty ( prefix + ".filter" ) ; if ( filterName != null ) { try { filter = ( Filter ) getCustomizeInstance ( filterName ) ; } catch ( Exception e1 ) { printInvalidPropMessage ( "filter" , filterName , e1 ) ; filter = ( Filter ) getDefaultInstance ( defaultFilter ) ; } } else { filter = ( Filter ) getDefaultInstance ( defaultFilter ) ; } String levelName = manager . getProperty ( prefix + ".level" ) ; if ( levelName != null ) { try { level = Level . parse ( levelName ) ; } catch ( Exception e ) { printInvalidPropMessage ( "level" , levelName , e ) ; level = Level . parse ( defaultLevel ) ; } } else { level = Level . parse ( defaultLevel ) ; } final String formatterName = manager . getProperty ( prefix + ".formatter" ) ; if ( formatterName != null ) { try { formatter = ( Formatter ) getCustomizeInstance ( formatterName ) ; } catch ( Exception e ) { printInvalidPropMessage ( "formatter" , formatterName , e ) ; formatter = ( Formatter ) getDefaultInstance ( defaultFormatter ) ; } } else { formatter = ( Formatter ) getDefaultInstance ( defaultFormatter ) ; } final String encodingName = manager . getProperty ( prefix + ".encoding" ) ; try { internalSetEncoding ( encodingName ) ; } catch ( UnsupportedEncodingException e ) { printInvalidPropMessage ( "encoding" , encodingName , e ) ; } }
target:  init the common properties, including filter, level, formatter, and encoding