IO InputStream、OutputStream：字节流读写类

java

FileInputStream：字节输入流

public static void main(String[] args) throws IOException {
            FileInputStream fis = new FileInputStream(new File("E:/a/a.txt"));
            /*
             * 1.使用前导入相应的包
             * 2.使用时要处理异常
             * 3.使用后要关闭流   fis.close()
             * */
            //读取文件内容
            //read()返回一个读到的字节
            System.out.println(fis.read());
            System.out.println(fis.read());
            //关闭流  
            fis.close();
    }

FileOutputStream：字节输出流

public static void main(String[] args) throws IOException {
        FileOutputStream fos = 
                new FileOutputStream(new File("E:/a/a.txt"),true);//追加 
        //输出文件内容
        fos.write(97);
        fos.write(98);
        fos.close();//关闭流  
    }

字节输入输出

基础使用

public static void main(String[] args) throws IOException {
        // 字节输入流
        FileInputStream fis = new FileInputStream("E:/a/a.txt");
        // 字节输出流
        FileOutputStream fos = new FileOutputStream("E:/a/b.txt");
        int a = -1;
        while ((a = fis.read()) != -1) {
            fos.write(a);
        }
        fis.close();
        fos.close();
    }

自定义缓冲区

public static void main(String[] args) throws IOException {
        // 字节输入流
        FileInputStream fis = new FileInputStream("E:/JavaTaskIO/guiyangtu.mp3");
        // 字节输出流
        FileOutputStream fos = new FileOutputStream("E:/JavaTaskIO/贵阳图.mp3");
        byte[] b = new byte[1024 * 2];// 创建篮子
        int length = 0;
        long time1 = System.currentTimeMillis();
        while ((length = fis.read(b)) != -1) {
            fos.write(b,0,length);
        }
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
        fis.close();
        fos.close();
    }

系统缓冲区

public class Test5_BufferdIOStream {
    public static void main(String[] args) throws Exception {
        //字节输入流
        FileInputStream fis = new FileInputStream("E:/JavaTaskIO/guiyangtu.mp3");
        //字节输出流
        FileOutputStream fos = new FileOutputStream("E:/JavaTaskIO/贵阳图.mp3");
        //创建一个带缓冲区的字节输入流
        BufferedInputStream bis = new BufferedInputStream(fis);
        //创建一个带缓冲区的字节输出流                            修改缓存区大小
        BufferedOutputStream bos = new BufferedOutputStream(fos,1024*200);
        long time1 = System.currentTimeMillis();
        int length = -1;
        while((length = bis.read())!=-1){
            bos.write(length);
        }
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
        //关闭流   
        fis.close();
        bos.close();
        bis.close();
        bos.close();
    }
}

DataInputStream && DataOutputStream：数据输入输出流

• 对对象的持久化存储，就是将自定的对象永久存储
• 这个过程叫序列化，在读出来，叫反序列化

public class Tset6_DataIOStream {
    public static void main(String[] args) throws Exception {
        FileOutputStream fos = new FileOutputStream("E:/JavaTaskIO/abc.txt");
        DataOutputStream dos = new DataOutputStream(fos);
        dos.writeInt(1234);
        dos.writeUTF("李四");
        dos.writeDouble(23.9);
        FileInputStream fis = new FileInputStream("E:/JavaTaskIO/abc.txt");
        DataInputStream dis = new DataInputStream(fis);
        //读的顺序跟写的顺序一样
        System.out.println(dis.readInt());
        System.out.println(dis.readUTF());
        System.out.println(dis.readDouble());
        fos.close();
        dos.close();
        fis.close();
        dis.close();
    }
}