question: public static String reqExpEscape ( String str ) { char [ ] arr = str . toCharArray ( ) ; StringBuilder sb = new StringBuilder ( str . length ( ) * 2 ) ; for ( int i = 0 ; i < arr . length ; i ++ ) { sb . append ( '\\' ) ; sb . append ( arr [ i ] ) ; } return sb . toString ( ) ; }
target:  escape all special characters of the regular expresson language