JAVA之IO學習（二）NIO

非阻塞式IO

• 使用channel代替stream
• 使用selector監控多條channel
• 可以在一個線程裏處理多個channel   I/O

Buffer解析

buffer既可以寫也可以讀，一開始我們向buffer寫入到了position位置個數據

 

現在想從buffer裏面讀出數據，調用buffer的flip()方法 調整爲讀模式
將position位置指向開始的位置。limit指向已有數據的尾部

讀完以後我們又想開始寫入數據到buffer,調用buffer的clear()方法，調整爲寫模式。limit指向capacity,position指向開始位置
clear()並沒有真正的清除數據只是調整了指針。

 

如果buffer未讀完。又想寫入。調用buffer的compact()方法，把未讀完的數據放到buffer前部，
將position指向未讀完數據的下面開始寫入

 

Channel解析 

selector 解析

在selector上註冊channel，監聽channel的狀態

代碼示例

package main.java.com.founder.study.javaio.nio;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/**
 * Created by Founder on 2020/6/28.
 */
interface FileCopyRunner {
    void copyFile(File source, File target);

}

public class FileCopyDemo{

    public static void main(String[] args) {

        FileCopyRunner noBufferStreamCopy = new FileCopyRunner() {
            @Override
            public void copyFile(File source, File target)  {
                FileInputStream in =null;
                FileOutputStream os = null;
                try {
                    in = new FileInputStream(source);
                   os = new FileOutputStream(target);
                    int result ;
                    while( (result = in.read()) != -1){
                        os.write(result);
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }finally {
                    close(os);
                    close(in);
                }
            }
        };

        FileCopyRunner bufferStreamCopy = new FileCopyRunner() {
            @Override
            public void copyFile(File source, File target) {
                FileInputStream in =null;
                FileOutputStream os = null;
                byte[] buffer =new byte[1024];
                try {

                    in = new FileInputStream(source);
                    os = new FileOutputStream(target);
                    int len ;
                    while( (len = in.read(buffer)) != -1){
                        os.write(buffer,0,len);
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }finally {
                    close(os);
                    close(in);
                }
            }
        };


        FileCopyRunner nioBufferCopy = new FileCopyRunner() {
            @Override
            public void copyFile(File source, File target) {
                FileChannel fin =null;
                FileChannel fout = null ;
                try {
                    fin= new FileInputStream(source).getChannel();
                    fout = new FileOutputStream(target).getChannel();
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    // 從channel中讀入數據寫進buffer
                    while (fin.read(buffer)!= -1){
                        //將buffer調整爲讀模式
                        buffer.flip();
                        //從buffer中讀出寫進寫進文件
                        while (buffer.hasRemaining()){
                            fout.write(buffer);

                        }
                        //循環讀完buffer後將buffer轉爲寫模式
                        buffer.clear();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    close(fin);
                    close(fout);
                }
            }
        };


        FileCopyRunner nioTransferCopy =  new FileCopyRunner() {
            @Override
            public void copyFile(File source, File target) {
                FileChannel fin =null;
                FileChannel fout = null;
                try {
                    fin = new FileInputStream(source).getChannel();
                    fout = new FileOutputStream(target).getChannel();
                    Long transferd = 0L;
                    while(transferd != fin.size()){
                        transferd +=fin.transferTo(0,fin.size(),fout);
                    }


                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    close(fin);
                    close(fout);
                }

            }
        };
    }

    private static void close(Closeable closeable) {
        try {
            closeable.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}