import sun.net.www.http.ChunkedInputStream; //导入依赖的package包/类
public synchronized long skip(long n) throws IOException {

        // REMIND: what does skip do on EOF????
        if (closed) {
            return 0;
        }

        if (in instanceof ChunkedInputStream) {
            n = in.skip(n);
        }
        else {
            // just skip min(n, num_bytes_left)
            long min = (n > expected - count) ? expected - count: n;
            n = in.skip(min);
        }
        justRead(n);
        return n;
    }