Download the pdf file from the server, http is OK, but https has not been tried

package com.cellstrain.icell.util;


import java.io. *;
import java.net.*;

public class DownloadPdf {

    /**
     * Download files from network Url
     * @param urlStr
     * @param fileName
     * @param savePath
     * @throws IOException
     */
    public static void  downLoadByUrl(String urlStr,String fileName,String savePath) throws IOException{
        URL url = new URL(urlStr);
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();
        //Set the timeout to 3 seconds
        conn.setConnectTimeout(5*1000);
        //Prevent the blocking program from grabbing and returning a 403 error
        conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
        // get the input stream
        InputStream inputStream = conn.getInputStream();
        //get own array
        byte[] getData = readInputStream(inputStream);
        //file save location
        File saveDir = new File (savePath);
        if(!saveDir.exists()){
            saveDir.mkdir ();
        }
        File file = new File(saveDir+File.separator+fileName);
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(getData);
        if(fos!=null){
            fos.close();
        }
        if(inputStream!=null){
            inputStream.close();
        }
        System.out.println("info:"+url+" download success");

    }


    /**
     * Get byte array from input stream
     * @param inputStream
     * @return
     * @throws IOException
     */
    public static  byte[] readInputStream(InputStream inputStream) throws IOException {
        byte[] buffer = new byte[1024];
        int len ​​= 0;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while((len = inputStream.read(buffer)) != -1) {
            bos.write(buffer, 0, len);
        }
        bos.close();
        return bos.toByteArray();
    }

    public static void main(String[] args) {
        try{
            downLoadByUrl("https://www.mybiosource.com/images/tds/protocol_samples/MBS700_Antibody_Set_Sandwich_ELISA_Protocol.pdf",
                    "ELISA.pdf","E:/upload/protocol");
        }catch (Exception e) {
            // TODO: handle exception
        }
    }
}

From: https://www.cnblogs.com/qianzf/p/6888357.html