question: private static String findFirstMatchingLine ( String data , String prefix ) { if ( data == null ) { return "" ; } int ix = data . indexOf ( prefix ) ; if ( ix >= 0 ) { int iy = data . indexOf ( "\n" , ix ) ; if ( iy > 0 ) { return data . substring ( ix , iy ) ; } } return "" ; }
target:  Filter the mappings and only return lines matching the prefix passed in.