字节流的操作

字符流：

FileReader

FileWriter

BufferedReader

BufferedWriter

-------------------------

字节流：

InpuStream

OutputStream

想要操作图片数据，这时就要用到字节流。

import java.io.*;

class FileStream 

{

    public static void main(String[] args) throws Exception 

    {

        //writeFile();    

        readFile3();

    }



    public static void writeFile()throws Exception{

        FileOutputStream fos = new FileOutputStream("fos.txt");



        fos.write("abcde".getBytes());

        fos.close();

    }



    public static void readFile1()throws Exception{

        FileInputStream fis = new FileInputStream("fos.txt");



        int ch = 0;

        while((ch = fis.read()) != -1){

            System.out.println((char)ch);

        }



        fis.close();

    }



    public static void readFile2()throws Exception{

        FileInputStream fis = new FileInputStream("fos.txt");



        byte[] buf = new byte[1024];

        int len = 0;

        while((len = fis.read(buf)) != -1){

            System.out.println(new String(buf, 0, len));

        }



        fis.close();

    }





    //available()

    //缺点：如果内容过大，容易占用内存，还是以第2种方法为主。

    public static void readFile3()throws Exception{

        FileInputStream fis = new FileInputStream("fos.txt");



        int num = fis.available();

        byte[] buf = new byte[num];//定义了一个刚刚好的缓冲区，不用再循环了

        fis.read(buf);

        System.out.println(new String(buf));

        fis.close();

    }

}