Java--> Implementing a breakpoint continuation (download)

--Breakpoint Continuation: Just like the Thunder download file, stop the download or close the program, the next time you download from the last place to continue, instead of starting from scratch ...

--Randomaccessfile---pointer (file pointer)--Seek (move file pointer)--the breakpoint continues

 PackageCom.dragon.java.downloadfile;ImportJava.io.File;Importjava.io.IOException;ImportJava.io.RandomAccessFile;/*Breakpoint Continuation: It is very important to download software! --First time download 100 bytes--Second Download 101 bytes ...  Find out where you left off the last time.  Where was the last time it was downloaded? Note the location of the breakpoint------> requires a third-party file to specifically remember the location of the breakpoint*/ Public classTest { Public Static voidMain (String args[]) {File srcfile=NewFile ("D:/java4android/01_java archaeological/01_java archaeology. mp4"); File Desdir=NewFile ("F:/vidio");    Copyfiletodir (Srcfile, Desdir); }     Public Static voidcopyfiletodir (file srcfile, file Desdir) {desdir.mkdirs (); //Creating a configuration fileFile ConfigFile =NewFile (Desdir, Srcfile.getname (). split ("\ \") [0]                + ". config"); //Create a target fileFile Desfile =NewFile (Desdir, Srcfile.getname ()); if(!configfile.exists () &&desfile.exists ()) {System.out.println ("The file has been downloaded!" "); return; } randomaccessfile rafsrc=NULL; Randomaccessfile Rafdes=NULL; Randomaccessfile Rafconfig=NULL; Try{rafsrc=NewRandomaccessfile (Srcfile, "R"); Rafdes=NewRandomaccessfile (Desfile, "RW"); Rafconfig=NewRandomaccessfile (ConfigFile, "RW"); //set the destination file as long as the source filerafdes.setlength (Srcfile.length ()); //set the file length of the configuration to 8 to prevent the first download from having an EOF exceptionRafconfig.setlength (8); //continue downloading from the location where you last downloaded!             Longpointer =Rafconfig.readlong (); System.out.println ("Downloaded:" + ((float) pointer/srcfile.length ())* 100 + "%");            Rafsrc.seek (pointer);            Rafdes.seek (pointer); //single transmission length set a small point, so as to observe whether the breakpoint continues to pass            byte[] buffer =New byte[32]; intLen =-1; //At the beginning of each copy, the pointer to the source file and the pointer to the target file must be read from the last disconnected position .             while(len = rafsrc.read (buffer))! =-1) {rafdes.write (buffer,0, Len); //when the profile is written, each time the file pointer is moved to its original location-so that it will only store the first 8 bytesRafconfig.seek (0); //each copy of the sum, hurriedly record the location of the file pointer, in case the breakpoint continued to use. Rafconfig.writelong (Rafsrc.getfilepointer ()); }        } Catch(IOException e) {System.out.println (e); } finally {            Try{rafsrc.close ();                Rafdes.close ();            Rafconfig.close (); } Catch(IOException e) {System.out.println (e); }            //Delete a profile after a stream is closedSystem.out.println ("Download successful! ");        Configfile.delete (); }    }}

--Copy to simulate a simple breakpoint continuation ...

Java--> Implementing a breakpoint continuation (download)