以下是使用FileInputStream类与FileOutputStream类复制文件。阅读以下代码,并将空处填写完整。import java.io.*;class Test2 { public static void main(String[] args) {String file1, file2;int ch = 0;file1 = "readme.txt";file2 = "readme.bak";try {FileInputStream fis = new; fos=new FileOutputStream(file2);int size= ;System.out.println("字节有效数、"+size);while ((ch = fis.read()) != -1) {System.out.write(ch);fos.write(ch);}fis.close();fos.close();} catch (IOException e) {System.out.println(e.toString());} }}