question: public Transfer writeString ( String s ) throws IOException { if ( s == null ) { out . writeInt ( - 1 ) ; } else { int len = s . length ( ) ; out . writeInt ( len ) ; for ( int i = 0 ; i < len ; i ++ ) { out . writeChar ( s . charAt ( i ) ) ; } } return this ; }
target:  Write a string. The maximum string length is Integer.MAX_VALUE.