下面红色部分 short num  用bb[0]<<8 | bb[1]  左移8位 在|bb[1]后面的8位 不是应该就可以了吗？
为什么还要bb[1] & 0xff 然后 num = num&0xFFFF;   呢？    谢谢给讲讲 最好举个列子  介绍我看看资料
import *;
public class ReaderDemo {
    public static void main(String[]args) {
        try {
            PushbackInputStream aa =new PushbackInputStream(new FileInputStream(args[0]));
            byte [] bb =new byte[2];
            ByteArrayInputStream cc =new ByteArrayInputStream(bb);
            InputStreamReader dd =new InputStreamReader(cc);
            int num =0;
            while(aa.read(bb)!=-1) {
                num =(short) ((bb[0]<<8) | (bb[1] & 0xff));
                num = num&0xFFFF;
                if(num >= 0xA440 && num < 0xFFFF) {
                    System.out.println("BIG5: "+(char) dd.read());
                    cc.reset();
                }
                else {
                    aa.unread(bb,1,1);
                    System.out.println("ASCII: "+(char) bb[0]);
                }
            }
            aa.close();
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
}

有没好心人给讲讲啊