java nio通过ByteBuffer输出文件信息

1.通过ByteBuffer的get()方法每次读取一个字节转换成char类型输出.

        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());

        }

2.使用系统字符集进行解码

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

System.getProperty可以获取系统字符集,可以用产生系统字符集的CharSet对象,来进行解码操作.

3.写入时进行编码

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());

ByteBuffer.wrap()方法将 ""UTF-16BE"编码的 byte 数组包装到缓冲区中,写入文件,转换成CharBuffer即可读取文件.

4.通过CharBuffer写入

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());

buff分配了24个字节,能储存12个字符,写入Some text可以通过FileInputStream获取的通道读取.