netty-tomcat-sample/rpc-tomcatv1/src/main/java/cn/hhj/nio/buffer/BufferDemo.java

package cn.hhj.nio.buffer;
import java.io.FileInputStream;
import java.nio.*;  
import java.nio.channels.*;  
  
public class BufferDemo {


    //put/get

    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, ByteBuffer 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();
    }
}