IO流(字节流File读写操作)

/*

字符流：

FileReader

FileWriter

BufferedReader

BufferedWriter

字节流：

InputStream OutputStream

需求，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 IOException
    {
        readFile_3();
    }
     
    public static void readFile_3()throws IOException
    {
        FileInputStream fis = new FileInputStream("fos.txt");
         
        // int num = fis.available();
        byte[] buf = new byte[fis.available()];//定义一个刚刚好的缓冲区。不用再循环了
         
        fis.read(buf);
         
        // System.out.println("num="+num);
        System.out.println(new String(buf));
         
        fis.close();
    }
     
    public static void readFile_2()throws IOException
    {
        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();
    }
     
    public static void readFile_1()throws IOException
    {
        FileInputStream fis = new FileInputStream("fos.txt");
    }
    public static void writeFile()throws IOException
    {
        FileOutputStream fos = new FileOutputStream("fos.txt");
         
        fos.write("abcde".getBytes());
    }
}