java 核心编程——IO流之字节流（二）

1.字节流

　　1.1字节流顾名思义就是操作字节的流。字节流是可以操作任意数据的，比如说媒体数据，音乐，电影，图片等，当然它也是可以操作字符的。字符流就是基于字节流来实现的，我们知道一个字节是8个二进制位，在UTF-8中一个字节对应一个英文字符，人们发现用单个字节操作文本比较麻烦，所以就对字节流进行封装，当对文本进行操作的时候就不直接对字节流进行操作，而直接对封装后的字节流也就是字符流进行操作，这样就比较方便。

　　1.2通过上述概述我们可以知道，使用字节流操作字符是完全行得通的。那么字符流是专门针对字符进行操作的，但是字符流能不能对除了字符以外的数据进行操作呢？

　　1.3如果你对除字符外的数据，比如说多媒体数据（音乐，电影，图片）进行操作，比如说复制一个音乐文件，程序编译时不会报错的，但是操作过程中可能会出现数据丢失的情况，当你复制结束打开该文件的时候，可能会因为数据的丢失而无法打开。所以强烈建议对字符文本的操作使用字符流，对字符以外的数据，使用字节流。

　　1.4字节流的基类：InputStream和OutputStream

2.字节流类图

　　2.1 InputStream类实现结构

　　

　　2.2 OutputStream 结构图

　　

3.常用类的具体使用

　　3.1字节数组作为输入输出源（ByteArrayInputStream和ByteArrayOutputStream）

package se.io;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class ByteArrayStream {

    public static void main(String[] args) {

        try {
            byte[] data = new byte[3];
            data[0] = 100;
            data[1] = 101;
            data[2] = 102;
            ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(data);
            byte[] buf = new byte[3];
            byteArrayInputStream.read(buf);
            System.out.println(new String(buf));

            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            byteArrayOutputStream.write(buf);
            System.out.println(byteArrayOutputStream.toString());

            byteArrayOutputStream.close();
            byteArrayInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

　　3.2文件作为输入输出源（FileInputStream 和FileOutputStream ）

package se.io;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileStream  {

    public static void main(String[] args) {

        try {
            FileInputStream fileInputStream = new FileInputStream("E:\test\file.txt");
            byte[] buf = new byte[3];
            fileInputStream.read(buf);

            FileOutputStream fileOutputStream = new FileOutputStream("E:\test\file3.txt");
            fileOutputStream.write(buf);

            fileOutputStream.close();
            fileInputStream.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

　　3.3 对象作为输入输出源（ObjectInputStream 和ObjectOutputStream ）

package se.io;

import java.io.*;
import java.util.Date;

public class ObjectStream {

    public static void main(String[] args) {

        try {
            FileOutputStream fileOutputStream = new FileOutputStream("E:\test\file.tmp");
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
            objectOutputStream.writeInt(100);
            objectOutputStream.writeObject("hello,world");
            objectOutputStream.writeObject(new Date());

            FileInputStream fileInputStream = new FileInputStream("E:\test\file.tmp");
            ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
            System.out.println(objectInputStream.readInt());
            System.out.println((String)objectInputStream.readObject());
            System.out.println((Date)objectInputStream.readObject());


        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

}

　　3.4管道作为输入输出源（PipedInputStream和PipedOutputStream）

package se.io;

import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;

public class PipedStream {

    public static void main(String[] args) {

            Sender sender = new Sender();
            PipedOutputStream pipedOutputStream = sender.getPipedOutputStream();

            Reciever reciever = new Reciever();
            PipedInputStream pipedInputStream = reciever.getPipedInputStream();

        try {
            pipedOutputStream.connect(pipedInputStream);
            new Thread(sender).start();
            new Thread(reciever).start();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}
//创建发送者类
class Sender extends Thread{
    private PipedOutputStream pipedOutputStream  = new PipedOutputStream();

    public  PipedOutputStream getPipedOutputStream(){
        return  pipedOutputStream;
    }

    public void run(){

        try {
            String s = new String("hello,receive you ");
            pipedOutputStream.write(s.getBytes());
            pipedOutputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}
//创建接受者类
class Reciever extends Thread{
    private PipedInputStream pipedInputStream = new PipedInputStream();

    byte[] buf = new byte[1024];

    public PipedInputStream getPipedInputStream() {
        return pipedInputStream;
    }

    public void run(){

        String s = null;
        byte[] rec = new byte[1024];
        try {
            int len = pipedInputStream.read(rec);
            s = new String(rec,0,len);
            System.out.println(s);
            pipedInputStream.close();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

　　3.5 缓存输入流输出流（BufferedInputStream 和BufferedOutputStream ）

package se.io;

import java.io.*;

public class BufferStream {

    public static void main(String[] args) {

        FileInputStream fileInputStream = null;
        try {
            fileInputStream = new FileInputStream("E:\test\file.txt");
            BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
            byte[] bytes = new byte[1024];
            int i = bufferedInputStream.read(bytes);

            FileOutputStream fileOutputStream = new FileOutputStream("E:\test\buffer.txt");
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
            bufferedOutputStream.write(bytes,0,i);

            bufferedOutputStream.close();
            bufferedInputStream.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

　　3.6 数据输入输出流（DataOutputStream 和DataInputStream ）

package se.io;

import java.io.*;

public class DataStream {

    public static void main(String[] args) {
        try {
            FileOutputStream fileOutputStream = new FileOutputStream("E:\test\data.txt");
            DataOutputStream dataOutputStream = new DataOutputStream(fileOutputStream);
            dataOutputStream.writeInt(123);
            dataOutputStream.writeBoolean(true);
            dataOutputStream.writeDouble(12.555);

            FileInputStream fileInputStream = new FileInputStream("E:\test\data.txt");
            DataInputStream dataInputStream = new DataInputStream(fileInputStream);

            int i = dataInputStream.readInt();
            boolean f = dataInputStream.readBoolean();
            double d = dataInputStream.readDouble();

            System.out.println(i);
            System.out.println(f);
            System.out.println(d);

            dataInputStream.close();
            fileInputStream.close();
            dataOutputStream.close();
            fileOutputStream.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}