question: public static String cidrMaskToNetMask ( String cidrMask ) { if ( cidrMask == null ) { return null ; } int cidrMaskValue = 0 ; try { cidrMaskValue = Integer . parseInt ( cidrMask ) ; } catch ( NumberFormatException e ) { return null ; } int cidrMaskFull = 0xffffffff << ( 32 - cidrMaskValue ) ; int cidrMaskBits1 = cidrMaskFull > > 24 & 0xff ; int cidrMaskBits2 = cidrMaskFull > > 16 & 0xff ; int cidrMaskBits3 = cidrMaskFull > > 8 & 0xff ; int cidrMaskBits4 = cidrMaskFull > > 0 & 0xff ; StringBuffer netMaskBuf = new StringBuffer ( ) ; netMaskBuf . append ( cidrMaskBits1 ) ; netMaskBuf . append ( '.' ) ; netMaskBuf . append ( cidrMaskBits2 ) ; netMaskBuf . append ( '.' ) ; netMaskBuf . append ( cidrMaskBits3 ) ; netMaskBuf . append ( '.' ) ; netMaskBuf . append ( cidrMaskBits4 ) ; return netMaskBuf . toString ( ) ; }
target:  Transforms a CIDR formatted mask into a regular network mask