阅读下列代码 import java.io.*;public class Example { public static void main(String[] args)throws Exception { File file = new File("itcast.txt"); FileInputStream in = new FileInputStream(file); byte[] buff = new byte[1024]; // 定义一个字节数组,作为缓冲区 int len; while ((len = in.________) != -1) { // 判断是否读到文件末尾 System.out.println(new String(buff,0,len)); } in.close(); }}请说出下划线上,填写的方法名称( )