nl_tokens: 获取两个路径从头部开始计算的交集
pl_tokens: public static String getIntersectPath ( String ph0 , String ph1 , String dft ) { // 木可能有交集
   if ( null == ph0 || null == ph1 ) return dft ; String [ ] ss0 = Strings . splitIgnoreBlank ( ph0 , "[\\\\/]" ) ; String [ ] ss1 = Strings . splitIgnoreBlank ( ph1 , "[\\\\/]" ) ; int pos = 0 ; int len = Math . <mask> ( ss0 . length , ss1 . length ) ; for ( ; pos < len ; pos ++ ) { if ( ! ss0 [ pos ] . equals ( ss1 [ pos ] ) ) break ; } // 木有交集
   if ( pos == 0 ) return dft ; // 得到
   String re = Lang . concat ( 0 , pos , "/" , ss0 ) . toString ( ) ; // 需要补全后面的 "/" 吗
   if ( ph0 . endsWith ( "/" ) && ph1 . endsWith ( "/" ) ) return re + "/" ; return re ; }