NiO example

public class Main3 {
    

    /** * nio Read the data in the file  * @param args */
    public static void main(String[] args) throws IOException {
    
        readThenWrite();
    }


    /** * nio Read the data in the file  *  file  -> channel -> buffer * @throws IOException */
    public static void read() throws IOException{
    
        //  Get input stream 
        FileInputStream fis = new FileInputStream("D:\\ideaProject\\helloWorld\\src\\main\\resources\\read.txt");
        //  Get access to 
        FileChannel readChannel = fis.getChannel();
        //  Create a 1024 Byte size buffer 
        ByteBuffer buf = ByteBuffer.allocate(1024);
        //  Read data from channel to buffer , And returns the number of bytes read 
        int readBytes = readChannel.read(buf);
        //  Number of bytes read is not equal to -1, Explain that there are data 
        while(readBytes != -1){
    
            byte[] bs = new byte[readBytes];
            //  Switch from write mode to read mode 
            buf.flip();
            //  The buffer still has data to read 
            while(buf.hasRemaining()){
    
                buf.get(bs);
                String str = new String(bs, 0, readBytes);
                System.out.println(str);
            }
            //  Clear buffer data 
            buf.clear();
            //  Read data from the channel to the buffer again , Know there's no data 
            readBytes = readChannel.read(buf);
        }
        fis.close();
    }


    /** *  write file   Existing problems , To be modified  * buffer -> channel ->  file  * @throws IOException */
    public static void write() throws IOException {
    
        FileOutputStream fos = new FileOutputStream("D:\\ideaProject\\helloWorld\\src\\main\\resources\\write.txt");
        FileChannel channel = fos.getChannel();
        ByteBuffer buf = ByteBuffer.allocate(1024);
        buf.put("2312312312".getBytes(StandardCharsets.UTF_8));
        System.out.println(buf.toString());
        int writeBytes = channel.write(buf);
        fos.close();
    }


    /** *  File replication  */
    public static void readThenWrite() throws IOException {
    
        FileInputStream fis = new FileInputStream("D:\\ideaProject\\helloWorld\\src\\main\\resources\\read.txt");
        FileOutputStream fos = new FileOutputStream("D:\\ideaProject\\helloWorld\\src\\main\\resources\\write.txt");
        FileChannel readChannel = fis.getChannel();
        FileChannel writeChannel = fos.getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        while(readChannel.read(buffer) != -1){
    
            //  Switch to read mode 
            buffer.flip();
            writeChannel.write(buffer);
            buffer.clear();
        }
        fis.close();
        fos.close();
    }

}