NIO组件之buffer

Java NIO指的是new IO ，相对OIO，也称non-blocking IO,对应四种基本IO类型中的IO多路复用，主要有有三大核心组件，Channel（管道），Buffer（缓冲区），selector（选择器)

基本操作如下注释：

package com.example.demo;

import java.nio.IntBuffer;

/**
 * Created by Administrator on 2019/9/22.
 */
public class NioTest {
    static IntBuffer intBuffer=null;
    public static void main(String[] args) {
        intBuffer=IntBuffer.allocate(20);//默认为写入模式
        print();//创建缓冲区p:l:c 0:20:20 p为position l为limit c为capacity
        put();//插入5个数
        print();//p:l:c  5:20:20 写入模式下写入数据只是改变postition的值
        get(2);//输出两个0
        print();//p:l:c 7:20:20 没有切换模式的情况下，get也变为在末尾添加两个0

        flip();//p:l:c 0:7:20 翻转，切换为读取模式
        get(4);

        print();//p:l:c 4:7:20
        get(2);
        print();//p:l:c 6:7:20
        clear();//p:l:c 0:20:20 切回写入模式，并清空
//        compact();//p:l:c 1:20:20 切回写入模式，保留未读取的数据
        print();



    }
    public static void put(){
        for (int i = 0; i < 5; i++) {
            intBuffer.put(i);
        }
        System.out.println("putting data");
    }

    public static void print(){
        System.out.println("position=="+intBuffer.position());
        System.out.println("limit=="+intBuffer.limit());
        System.out.println("capacity=="+intBuffer.capacity());
    }
    public static void flip(){
        intBuffer.flip();
        System.out.println("flipping");
    }
    public static void clear(){
        intBuffer.clear();
        System.out.println("clearing the buffer");
    }
    public static void compact(){
        intBuffer.compact();
        System.out.println("compacting the buffer");
    }
    public static void get(int n){
        System.out.println("starting to read");
        for (int i = 0; i < n; i++) {
            System.out.println("read data=="+intBuffer.get());
        }
        System.out.println("ending to read");
    }
}

输出

position==0
limit==20
capacity==20
putting data
position==5
limit==20
capacity==20
starting to read
read data==0
read data==0
ending to read
position==7
limit==20
capacity==20
flipping
starting to read
read data==0
read data==1
read data==2
read data==3
ending to read
position==4
limit==7
capacity==20
starting to read
read data==4
read data==0
ending to read
position==6
limit==7
capacity==20
clearing the buffer
position==0
limit==20
capacity==20