public IStringBuffer append ( String str ) { if ( str == null ) throw new NullPointerException ( ) ; //check the necessary to resize the buffer. if ( count + str . length ( ) > buff . length ) { resizeTo ( ( count + str . length ( ) ) * 2 + 1 ) ; } for ( int j = 0 ; j < str . length ( ) ; j ++ ) { buff [ count ++ ] = str . charAt ( j ) ; } return this ; }
append a string to the buffer