获取远程文件大小 getContentLength()为-1之谜

获取远程文件大小 网上给的方案大部分是下面这条，但是会出现getContentLength()为-1的情况，搜索结果大部分为
conn.setRequestProperty("Accept-Encoding", "identity");
这条建议，但无效果

        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection) url1.openConnection();
        conn.setRequestProperty("Accept-Encoding", "identity");
        long contentLength = conn.getContentLength();
        conn.disconnect();
        return contentLength;

看一下源码恍然大悟
看一下下面两段代码就知道了

    public int getContentLength() {
        long l = getContentLengthLong();
        if (l > Integer.MAX_VALUE)
            return -1;
        return (int) l;
    }
    
    
    public long getContentLengthLong() {
        return getHeaderFieldLong("content-length", -1);
    }

返回Long就可以了

        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection) url1.openConnection();
        conn.setRequestProperty("Accept-Encoding", "identity");
        long contentLength = conn.getContentLengthLong();
        conn.disconnect();
        return contentLength;