java nio通過ByteBuffer輸出文件信息

1.通過ByteBuffer的get()方法每次讀取一個字節轉換成char類型輸出.

        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.使用系統字符集進行解碼

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

System.getProperty可以獲取系統字符集,可以用產生系統字符集的CharSet對象,來進行解碼操作.

3.寫入時進行編碼

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()方法將 ""UTF-16BE"編碼的 byte 數組包裝到緩沖區中,寫入文件,轉換成CharBuffer即可讀取文件.

4.通過CharBuffer寫入

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個字節,能儲存12個字符,寫入Some text可以通過FileInputStream獲取的通道讀取.