question: public char [ ] toCharArray ( int startIndex , int endIndex ) { endIndex = validateRange ( startIndex , endIndex ) ; int len = endIndex - startIndex ; if ( len == 0 ) { return ArrayUtils . EMPTY_CHAR_ARRAY ; } char chars [ ] = new char [ len ] ; System . arraycopy ( buffer , startIndex , chars , 0 , len ) ; return chars ; }
target:  Copies part of the builder's character array into a new character array.