String s = "1234567890abcdefg";
byte[] b = s.getBytes();
ByteArrayInputStream bis = new ByteArrayInputStream(b); //输入流
ByteArrayOutputStream bos = new ByteArrayOutputStream(); //输出流
bos.write(b, 0, b.length); //写到输出流

------解决方案--------------------
   		ByteArrayInputStream bis = new ByteArrayInputStream("abcdef".getBytes());

		ByteArrayOutputStream bos = new ByteArrayOutputStream();

		int ch = 0;
		while ((ch = bis.read()) != -1) {
			bos.write(ch);
		}