package com.lf.io;

import java.io.FileInputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class BufferDemo {
    public static void main(String args[]) throws Exception {
        //这用用的是文件 IO 处理
        FileInputStream fin = new FileInputStream("E://test.txt");
        //创建文件的操作管道
        FileChannel fc = fin.getChannel();
        //分配一个 10 个大小缓冲区，说白了就是分配一个 10 个大小的 byte 数组
        ByteBuffer buffer = ByteBuffer.allocate(10);
        output("初始化", buffer);
        //先读一下
        fc.read(buffer);
        output("调用 read()", buffer);
        //准备操作之前，先锁定操作范围
        buffer.flip();
        output("调用 flip()", buffer);
        //判断有没有可读数据
        while (buffer.remaining() > 0) {
            byte b = buffer.get();
            System.out.print(((char) b));
        }
        output("调用 get()", buffer);
        //可以理解为解锁
        buffer.clear();
        output("调用 clear()", buffer);
        //最后把管道关闭
        fin.close();
    }

    //把这个缓冲里面实时状态给答应出来
    public static void output(String step, Buffer buffer) {
        System.out.println(step + " : ");
        //容量，数组大小
        System.out.print("capacity: " + buffer.capacity() + ", ");
        //当前操作数据所在的位置，也可以叫做游标
        System.out.print("position: " + buffer.position() + ", ");
        //锁定值，flip，数据操作范围索引只能在 position - limit 之间
        System.out.println("limit: " + buffer.limit());
        System.out.println();
    }
}

初始化 : 
capacity: 10, position: 0, limit: 10

调用 read() : 
capacity: 10, position: 4, limit: 10

调用 flip() : 
capacity: 10, position: 0, limit: 4

LFGB调用 get() : 
capacity: 10, position: 4, limit: 4

调用 clear() : 
capacity: 10, position: 0, limit: 10


Process finished with exit code 0