java nio通过ByteBuffer输出文件信息

        fc = new FileInputStream("src/demo20/data.txt").getChannel();
        ByteBuffer buff = ByteBuffer.allocate(BSIZE);
        buff = ByteBuffer.allocateDirect(BSIZE);
        fc.read(buff);
        buff.flip();
        while (buff.hasRemaining()) {
            System.out.print((char)buff.get());
        }

FileChannel fc = new FileOutputStream("src/demo20/data2.txt").getChannel();
        fc.write(ByteBuffer.wrap("Some text".getBytes()));
buff.rewind();
String encoding = System.getProperty("file.encoding");//获取系统字符集
System.out.println("Decoded using "+ encoding + ":" + Charset.forName(encoding).decode(buff));//Decoded using GBK:Some text

fc = new FileOutputStream("src/demo20/data2.txt").getChannel();
        fc.write(ByteBuffer.wrap("Some text".getBytes("UTF-16BE")));
        fc.close();
        fc = new FileInputStream("src/demo20/data2.txt").getChannel();
        buff.clear();
        fc.read(buff);
        buff.flip();
        System.out.println(buff.asCharBuffer());

fc = new FileOutputStream("src/demo20/data2.txt").getChannel();
        buff = ByteBuffer.allocate(24);
        buff.asCharBuffer().put("Some text");
        fc.write(buff);
        fc.close();
        fc = new FileInputStream("src/demo20/data2.txt").getChannel();
        buff.clear();
        fc.read(buff);
        buff.flip();
        System.out.println(buff.asCharBuffer());