字节流

字节流

字节流的父类(抽象类)：

InputStream：字节输入流

1.public int read() {}

2.public int read (byte[] b) {}

3.public int read(byte[] b, int off, int len) {}

OutputStream：字节输出流

1.public void write(int n) {}

2.public void write(byte[] b) {}

3.public void write(byte[] b, int off, int len) {}

文件字节流

FileInputStream：

public int read(byte[] b)  //从流中读取多个字节，将读到内容存入b数组，返回实际读到的字节数；如果达到文件的尾部，则返回-1

eg : 

public class Demo01 {
    public static void main(String[] args) throws IOException {
        //1.创建FileInputStream，并指定文件路径
        FileInputStream fis = new FileInputStream("g:\\aaa.txt");
        //2.读取文件
        byte[] buf = new byte[3];
        int count = 0;
        while((count = fis.read(buf))!=-1){
            System.out.println(new String(buf,0,count));
        }
        //3.关闭
        try {
            fis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("执行完毕");
    }
}

FileOutputStream：

public void write(byte[] b)  //一次写多个字节，将b数组中所有字节，写入输出流

eg : 

public class Demo02 {
    public static void main(String[] args) throws IOException {
        //1.创建文件字节输出流对象
        FileOutputStream fos = new FileOutputStream("g:\\bbb.txt",true);
        //2.写入文件
        //fos.write(97);
        //fos.write('b');
        //fos.write('c');
        String string = "helloworld";
        fos.write(string.getBytes());
        //3.关闭
        fos.close();
        System.out.println("执行完毕");
    }
}

/**
 * 使用文件字节流实现文件的复制
 * @author
 */
public class Demo03 {
    public static void main(String[] args) throws IOException {
        //1.创建流
        //1.1文件字节输入流
        FileInputStream fis = new FileInputStream("g:\\001.png");
        //1.2文件字节输出流
        FileOutputStream fos = new FileOutputStream("g:\\002.png");
        //2.一边读，一边写
        byte[] buf = new byte[1024];
        int count = 0;
        while((count = fis.read(buf))!=-1){
            fos.write(buf,0,count);
        }
        //3.关闭
        fis.close();
        fos.close();
        System.out.println("复制完毕");
    }
}

字节缓冲流

缓冲流：BufferedInputStream/Buffered0utputStream

提高I0效率，减少访问磁盘的次数

数据存储在缓冲区中，flush是将缓存区的内容写入文件中，也可以直接close

eg : 

public class Demo04 {
    public static void main(String[] args) throws IOException {
        //1.创建BufferedInputStream
        FileInputStream fis = new FileInputStream("g:\\aaa.txt");
        BufferedInputStream bis = new BufferedInputStream(fis);
        //2.读取
        /*int data = 0;
        while((data = bis.read())!=-1){
            System.out.print((char)data);
        }*/
        byte[] buf = new byte[1024];
        int count = 0;
        while((count = bis.read(buf))!=-1){
            System.out.println(new String(buf,0,count));
        }
        //3.关闭
        bis.close();
    }
}

public class Demo05 {
    public static void main(String[] args) throws IOException {
        //1.创建字节输出缓冲流
        FileOutputStream fos = new FileOutputStream("g:\\buffer.txt");
        BufferedOutputStream bos = new BufferedOutputStream(fos);
        //2.写入文件
        for (int i = 0; i < 10; i++) {
            bos.write("helloworld\r\n".getBytes());//写入8K缓冲区
            bos.flush();//刷新到硬盘
        }
        //3.关闭(内部调用flush)
        bos.close();
    }
}