1.概要

准备学一下Netty,先从NIO的三大组件开始。先ByteBuffer

2.代码

2.1 主函数 

package com.xjc.springcloundtest;import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;public class Main {public static void main(String[] args) throws IOException {FileChannel channel = new FileInputStream("4.txt").getChannel();ByteBuffer byteBuffer = ByteBuffer.allocate(10);while (true){int len = channel.read(byteBuffer);System.out.println("读取的字节数:"+len);if(len==-1){break;}byteBuffer.flip();while (byteBuffer.hasRemaining()){byte b = byteBuffer.get();System.out.println((char)b);}byteBuffer.clear();}System.out.println("Hello world!");}
}

2.2 准备的文件（4.txt）

123456789abc

3.运行结果

C:\Users\ThinkPad\.jdks\openjdk-21.0.2\bin\java.exe "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2023.3.2\lib\idea_rt.jar=51792:D:\Program Files\JetBrains\IntelliJ IDEA 2023.3.2\bin" -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8 -classpath C:\Users\ThinkPad\IdeaProjects\untitled12\target\classes com.xjc.springcloundtest.Main
读取的字节数:10
1
2
3
4
5
6
7
8
9
a
读取的字节数:2
b
c
读取的字节数:-1
Hello world!Process finished with exit code 0