byte[] buf = new byte[1024];//time to make zip file
    String zipName="";
    ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipName));

    for(int i=0; i<copy.length; i++){//put all pdfs in the zip
        FileInputStream zipFile = new FileInputStream(copy[i]);
        out.putNextEntry(new ZipEntry(copy[i]));
        int len;
            out.write(buf, 0, len);             
copy is an array of strings which contain the file path for each file I want (for example C:\files\test.pdf, I have tested it yes the correct values are in it). It compiles and runs fine with no exceptions and creates the zip folder, but nothing is in said zip folder.

Note, I also have an array of files (which I used to fill copy using toString) if that would be easier. ZipEntry only seems to accept strings which is why I tried to do it this way.