io包是以字節(jié)流(stream)、字符流(reader/writer)來進(jìn)行文件的同步讀寫。
nio是以通道（channel）的方式進(jìn)行一步讀取。是JDK4以后提出遥缕，從寫法或者類庫上都比io簡潔，但必須依賴于io來創(chuàng)建宵呛。
舊io的文件復(fù)制：

BufferedReader br = new BufferedReader(new FileReader(new File(path)));
        PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(path + "z")));
        String s;
        while ((s = br.readLine())!=null){
            pw.write(s+"\n");
        }
        br.close();
        pw.close();

nio的文件復(fù)制：

FileChannel in = new FileInputStream("../fc.in").getChannel();
            FileChannel out = new FileOutputStream("../fc.out1").getChannel();
//type 1:
//            ByteBuffer buffer = ByteBuffer.allocate(GetChannel.BSIZE);
//            while (in.read(buffer)!=-1){
//                buffer.flip();
//                out.write(buffer);
//                buffer.clear();
//            }

            //type 2:
            in.transferTo(0,in.size(),out);
            //type 3:
            out.transferFrom(in,0,in.size());

nio在讀入文件時(shí)，需要依靠ByteBuffer來存儲(chǔ)讀到的字節(jié)數(shù)組夕凝，ByteBuffer.flip()可以開啟快速存取模式(將當(dāng)前位置置0)宝穗，每次讀取完下一次讀取前需要清除緩存ByteBuffer.clear()。
-- 在ByteBuffer中码秉，asCharBuffer()方法會(huì)將字節(jié)以字符的形式輸出逮矛。該方法存在弊端：

public class BufferToText {
    public static int BSIZE=1024;
    static String path="../data2.out";
    public static void main(String[] args) throws IOException {
        FileChannel fc = new FileOutputStream(path).getChannel();
        fc.write(ByteBuffer.wrap("wa haha haha    \n".getBytes()));//write sth
        fc.close();
        //Read the file
        fc = new FileInputStream(path).getChannel();
        ByteBuffer buff = ByteBuffer.allocate(BSIZE);
        fc.read(buff);
        buff.flip();
        System.out.println(buff.asCharBuffer());//此處采用JAVA默認(rèn)的UTF-16BE來轉(zhuǎn)換，會(huì)亂碼
        buff.rewind();
        String encoding = System.getProperty("file.encoding");//the current java file's encoding.
        //此處不會(huì)亂碼转砖，因?yàn)椴捎孟到y(tǒng)默認(rèn)的編碼編寫须鼎，此處采用系統(tǒng)默認(rèn)編碼解碼
        System.out.println("Decoded using"+encoding+":"+ Charset.forName(encoding).decode(buff));
//-------------------------------------------------
        fc = new FileOutputStream(path).getChannel();
        fc.write(ByteBuffer.wrap(("hanhong hui huahua ").getBytes("UTF-16be")));
        fc.close();

        //re-read
        fc = new FileInputStream(path).getChannel();
        buff.clear();
        fc.read(buff);
        buff.flip();

        System.out.println(buff.asCharBuffer());
        //------------------------------------------------

        fc = new FileOutputStream(path).getChannel();
        buff = ByteBuffer.allocate(100);
        buff.asCharBuffer().put("ai xiong xiong    ");
        fc.write(buff);
        fc.close();

        //read and display
        fc = new FileInputStream(path).getChannel();
        buff.clear();
        fc.read(buff);
        buff.flip();
        System.out.println(buff.asCharBuffer());
    }
}