假设存在xxx.txt文件,内容为”大家好”,以下代码运行的结果为?( ) public static void main(String[] args) throws IOException { FileReader fr = new FileReader( "xxx.txt" ); FileWriter fw = new FileWriter( "zzz.txt" ); int c; while ((c = fr.read()) != -1) { fw. write (); } fr.close(); fw.close(); }