1、操作文件基本演示

写

public class Demo8 {

    public static void main(String[] args) throws IOException {

        //创建字节输出流对象
        FileOutputStream fos = new FileOutputStream("demo.txt");

        //数据直接写入目标文件，没有缓冲区
        fos.write("aaaaaddfsdss".getBytes());

        fos.close();

    }

}

逐个字节读取

public class Demo9 {

public static void main(String[] args) throws IOException {

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

    int ch = 0;
    while((ch = fis.read()) != -1) {
        System.out.println((char)ch);
    }

    fis.close();
}

}

逐个数组读取

public class Demo10 {

    public static void main(String[] args) throws IOException {

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

        byte[] buf = new byte[1024];
        int length = 0;

        while((length = fis.read(buf, 0, length)) != -1) {
            System.out.println(new String(buf,0,length));
        }

        fis.close();

    }

}

2、练习 - 复制mp3

直接复制

public class Demo11 {

    public static void main(String[] args) throws IOException {

        FileInputStream fis = new FileInputStream("0.mp3");
        FileOutputStream fos = new FileOutputStream("1.mp3");

        byte[] buf = new byte[1024];
        int length = 0;

        while((length = fis.read()) != -1) {
            fos.write(buf,0,length);
        }

        fos.close();
        fis.close();
    }

}

高效复制

public class Demo11 {

    public static void main(String[] args) throws IOException {

        FileInputStream fis = new FileInputStream("0.mp3");
        BufferedInputStream bufis = new BufferedInputStream(fis);

        FileOutputStream fos = new FileOutputStream("1.mp3");
        BufferedOutputStream bufos = new BufferedOutputStream(fos);

        byte[] buf = new byte[1024];

        int length = 0;
        while((length = bufis.read(buf)) != -1) {
            bufos.write(buf, 0, length);
        }

        bufis.close();
        bufos.close();

    }
}

3、演示键盘录入

读取键盘录入的一个数据，并打印在控制台上。

键盘本身就是一个标准的输入设备。

对于java而言，对于这种输入设备都有相应的对象。

java.lang包里的 System类

public static finael InputStream in

“标准”输入流，不用关闭。

键盘录入：

public class Demo12 {
    public static void main(String[] args) throws IOException {
        InputStream in = System.in;
        int ch = in.read();
        System.out.println(ch);
    }
}

读取键盘录入：

public class Demo15 {

    public static void main(String[] args) throws IOException {

        InputStream in = System.in;
        int ch = 0;
        StringBuilder sb = new StringBuilder();
        while((ch=in.read())!=-1) {
            if(ch=='\r') 
                continue;
            if(ch=='\n') {
                String temp = sb.toString();
                if("over".equals(temp))
                    break;
                System.out.println(temp.toUpperCase());
                sb.delete(0, sb.length());
            } else {
                sb.append((char)ch);
            }
        }

    }

}