Downloading file/files in Java. Multithreading, this works? -

first, needs know i'm relatively new java coding. more precise i'm new object oriented programming.

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to question.

i trying create download class updates progress bar given show progress. , possibly else decide give in future update.

the issue that, in head, shouldn't work. can want on "main" method , gui still responsive , quick. in experience in past programming, not possible unless thread gui. why this?

since works, ok way?

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class main

package atomicelectronics;  import java.io.ioexception;  import atomicelectronics.physical.atomframe; import atomicelectronics.utility.download;  public class initial {      static atomframe atomlauncher;      public static void main(string[] args) {          atomlauncher = new atomframe();         atomlauncher.start();          system.out.println(integer.max_value);          download thedownload = new download();         thedownload.fileprogressbar(atomlauncher.progressbar);         try {             thedownload.exicute("http://download.videolan.org/pub/videolan/vlc/last/win64/vlc-2.1.3-win64.exe", "c:\\users\\trinaryatom\\appdata\\roaming");         } catch (ioexception e) {             // todo auto-generated catch block             e.printstacktrace();         }          // todo add download methods         // thedownload.updatebartotal(jprogressbar);         // thedownload.updatelabelspeed(string);         // thedownload.updatelabeltotal(string);         // thedownload.addfile(file);         // thedownload.addfiles(files);     }  } 

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class atomframe

package atomicelectronics.physical;  import javax.swing.jframe; import java.awt.flowlayout; import javax.swing.jprogressbar;  public class atomframe extends jframe{      public jprogressbar progressbar;      private static final long serialversionuid = 4010489530693307355l;      public static void main(string[] args){         atomframe testframe = new atomframe();         testframe.start();     }      public atomframe(){         initializecomponents();     }      public void initializecomponents(){         this.setsize(400, 400);         this.setlocationrelativeto(null);         this.setdefaultcloseoperation(jframe.exit_on_close);         this.settitle("atom launcher");         this.setlayout(new flowlayout(flowlayout.center, 5, 5));          progressbar = new jprogressbar();         this.add(progressbar);          //this.pack();     }      public void start() {         this.setvisible(true);     }      public void close() {         this.dispose();     } } 

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class download

package atomicelectronics.utility;  import java.io.file; import java.io.fileoutputstream; import java.io.ioexception; import java.io.inputstream; import java.net.httpurlconnection; import java.net.url;  import javax.swing.jprogressbar;  public class download {      private static final int buffer_size = 4096;     private jprogressbar fileprogressbar;      public download() {     }      public void fileprogressbar(jprogressbar filebar) {         fileprogressbar = filebar;     }      public void exicute(string fileurl, string savedir) throws ioexception  {          url url = new url(fileurl);         httpurlconnection httpconn = (httpurlconnection) url.openconnection();         int responsecode = httpconn.getresponsecode();          // check http response code first         if (responsecode == httpurlconnection.http_ok) {             string filename = "";             string disposition = httpconn.getheaderfield("content-disposition");             string contenttype = httpconn.getcontenttype();             double contentlength = httpconn.getcontentlength();              if (disposition != null) {                 // extracts file name header field                 int index = disposition.indexof("filename=");                 if (index > 0) {             filename = disposition.substring(index + 9,                         disposition.length());             }         } else {             // extracts file name url             filename = fileurl.substring(fileurl.lastindexof("/") + 1,                     fileurl.length());         }          system.out.println("content-type = " + contenttype);         system.out.println("content-disposition = " + disposition);         system.out.println("content-length = " + contentlength);         system.out.println("filename = " + filename);          // opens input stream http connection         inputstream inputstream = httpconn.getinputstream();         string savefilepath = savedir + file.separator + filename;          // opens output stream save file         fileoutputstream outputstream = new fileoutputstream(savefilepath);          double totalread = 0;         int bytesread = -1;         byte[] buffer = new byte[buffer_size];         while ((bytesread = inputstream.read(buffer)) != -1) {             outputstream.write(buffer, 0, bytesread);             totalread += bytesread;             system.out.println((totalread / contentlength) * 100);             fileprogressbar.setvalue((int)((totalread / contentlength) * 100));         }          outputstream.close();         inputstream.close();          system.out.println("file downloaded");     } else {         system.out.println("no file download. server replied http code: " + responsecode);     }     httpconn.disconnect();  } 

}

suggestions:

• use swingworker background thread work.
• inside swingworker, set progress "bound" property via setprogress(int progress). value should between 1 , 100.
• don't have swingworker/file downloader hold jprogressbar or swing components.
• add propertychangelistener swingworker , monitor changes in progress property.
• never make swing fields (or , and fields) public. limit access, , instead change object state via methods.
• read tutorial concurrency in swing necessary details.

for example, code below gross simplification , downloads no files, should give idea:

import java.awt.*; import java.beans.propertychangeevent; import java.beans.propertychangelistener; import java.util.random;  import javax.swing.*;  public class initial {     static atomframe atomlauncher;     public static void main(string[] args) {        atomlauncher = new atomframe();       atomlauncher.start();        system.out.println(integer.max_value);        final download thedownload = new download();       thedownload.addpropertychangelistener(new propertychangelistener() {           @override          public void propertychange(propertychangeevent pcevt) {             if ("progress".equals(pcevt.getpropertyname())) {                int progress = thedownload.getprogress();                atomlauncher.setprogress(progress);             }          }       });        thedownload.execute();    }  }  class atomframe extends jframe {     // ********* should private!    private jprogressbar progressbar;     private static final long serialversionuid = 4010489530693307355l;     public static void main(string[] args) {       atomframe testframe = new atomframe();       testframe.start();    }     public void setprogress(int progress) {       progressbar.setvalue(progress);    }     public atomframe() {       initializecomponents();    }     public void initializecomponents() {       this.setsize(400, 400);       this.setlocationrelativeto(null);       this.setdefaultcloseoperation(jframe.exit_on_close);       this.settitle("atom launcher");       this.setlayout(new flowlayout(flowlayout.center, 5, 5));        progressbar = new jprogressbar();       this.add(progressbar);        // this.pack();    }     public void start() {       this.setvisible(true);    }     public void close() {       this.dispose();    } }  class download extends swingworker<void, void> {    private static final long sleep_time = 300;    private random random = new random();     @override    protected void doinbackground() throws exception {       int myprogress = 0;       while (myprogress < 100) {          myprogress += random.nextint(10);          setprogress(myprogress);          try {             thread.sleep(sleep_time);          } catch (interruptedexception e) {}       }       return null;    } }