NIO的开发使用--学习孙哥&不良人课程，整理学习笔记文章

5. NIO的开发使用

5.1 文件操作

5.1.1 读取文件内容

1. 第一个程序 读文件的内容，读Buffer---> String ---->程序中使用了

public class TestNIO1 {
    public static void main(String[] args) throws IOException {
        //1 创建Channel通道  FileChannel
        FileChannel channel = new FileInputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data.txt").getChannel();

        //2 创建缓冲区
        //1234567890
        ByteBuffer buffer = ByteBuffer.allocate(10);

        while (true) {
            //3把通道内获取的文件数据，写入缓冲区
            int read = channel.read(buffer);

            if (read == -1) break;

            //4.程序读取buffer内容，后续的操作。设置buffer为读模式。
            buffer.flip();

            //5.循环读取缓冲区中的数据
            while (buffer.hasRemaining()) {
                byte b = buffer.get();
                System.out.println("(char)b = " + (char) b);
            }
          
            //Charset.forName("UTF-8").decode(buffer).toString ---> String

            //6. 设置buffer的写模式
            buffer.clear();
        }
    }
}

5.1.2 写入文件内容

public class TestNIO11 {
    public static void main(String[] args) throws IOException {


        //1 获得Channel  FileOutputStream, RandomAccessFile
        FileChannel channel = new FileOutputStream("data1").getChannel();

        //2 获得Buffer
        ByteBuffer buffer = Charset.forName("UTF-8").encode("sunshuai");

        //3write
        channel.write(buffer);

    }

5.1.3 文件的复制

public class TestNIO12 {
    public static void main(String[] args) throws IOException {
        //data---data2
      /*  FileInputStream inputStream = new FileInputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data.txt");
        FileOutputStream fileOutputStream = new FileOutputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data2.txt");

        byte[] buffer = new byte[1024];

        while (true) {
            int read = inputStream.read(buffer);
            if (read == -1) break;
            fileOutputStream.write(buffer, 0, read);
        }*/

       /* FileInputStream inputStream = new FileInputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data.txt");
        FileOutputStream fileOutputStream = new FileOutputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data2.txt");

        IOUtils.copy(inputStream,fileOutputStream);*/

        FileChannel from = new FileInputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data.txt").getChannel();
        FileChannel to = new FileOutputStream("/Users/sunshuai/Develop/code/java/idea/netty-proj-lession/netty-basic-01/data2.txt").getChannel();

        //传输数据上线的 2G-1
        // 若果实际文件大小就是超过2G 如何进行文件的copy
        //from.transferTo(0, from.size(), to);

        long left = from.size();
        while (left > 0) {
            left = left - from.transferTo(from.size()-left, left, to);
        }


    }
}