question: public static String combineExtensions ( final String [ ] extensions ) { Check . notNull ( extensions , "extensions" ) ; final StringBuffer ret = new StringBuffer ( ) ; for ( int i = 0 ; i < extensions . length ; i ++ ) { if ( i > 0 ) { ret . append ( ", " ) ; } ret . append ( extensions [ i ] ) ; } return ret . toString ( ) ; }
target:  Combines the given extensions strings into a single string, extensions separated by a comma.