Crear tu cuenta atrás en JavaScript
javaScript countdown/count-up code (copy and paste to your Web page):

TargetDate = "12/31/2020 5:00 AM";BackColor = "palegreen";ForeColor = "navy";CountActive = true;CountStepper = -1;LeadingZero = true;DisplayFormat = "%%D%% Days, %%H%% Hours, %%M%% Minutes, %%S%% Seconds.";FinishMessage = "It is finally here!";

//countdown.js file//

/*Author: Robert Hashemianhttp://www.hashemian.com/

You can use this code in any manner so long as the author'sname, Web address and this disclaimer is kept intact.********************************************************Usage Sample:

TargetDate = "12/31/2020 5:00 AM";BackColor = "palegreen";ForeColor = "navy";CountActive = true;CountStepper = -1;LeadingZero = true;DisplayFormat = "%%D%% Days, %%H%% Hours, %%M%% Minutes, %%S%% Seconds.";FinishMessage = "It is finally here!";

*/

function calcage(secs, num1, num2) {  s = ((Math.floor(secs/num1))%num2).toString();  if (LeadingZero && s.length < 2)    s = "0" + s;  return "" + s + "";}

function CountBack(secs) {  if (secs < 0) {    document.getElementById("cntdwn").innerHTML = FinishMessage;    return;  }  DisplayStr = DisplayFormat.replace(/%%D%%/g, calcage(secs,86400,100000));  DisplayStr = DisplayStr.replace(/%%H%%/g, calcage(secs,3600,24));  DisplayStr = DisplayStr.replace(/%%M%%/g, calcage(secs,60,60));  DisplayStr = DisplayStr.replace(/%%S%%/g, calcage(secs,1,60));

  document.getElementById("cntdwn").innerHTML = DisplayStr;  if (CountActive)    setTimeout("CountBack(" + (secs+CountStepper) + ")", SetTimeOutPeriod);}

function putspan(backcolor, forecolor) { document.write("");}

if (typeof(BackColor)=="undefined")  BackColor = "white";if (typeof(ForeColor)=="undefined")  ForeColor= "black";if (typeof(TargetDate)=="undefined")  TargetDate = "12/31/2020 5:00 AM";if (typeof(DisplayFormat)=="undefined")  DisplayFormat = "%%D%% Dias, %%H%%:%%M%%,%%S%%";if (typeof(CountActive)=="undefined")  CountActive = true;if (typeof(FinishMessage)=="undefined")  FinishMessage = "";if (typeof(CountStepper)!="number")  CountStepper = -1;if (typeof(LeadingZero)=="undefined")  LeadingZero = true;

CountStepper = Math.ceil(CountStepper);if (CountStepper == 0)  CountActive = false;var SetTimeOutPeriod = (Math.abs(CountStepper)-1)*1000 + 990;putspan(BackColor, ForeColor);var dthen = new Date(TargetDate);var dnow = new Date();if(CountStepper>0)  ddiff = new Date(dnow-dthen);else  ddiff = new Date(dthen-dnow);gsecs = Math.floor(ddiff.valueOf()/1000);CountBack(gsecs);

Publicado en Java

Descomprimir archivos comprimidos Zip usando las librerías nativas de java.

import java.io.*;import java.util.zip.*;

public class UnZip {
   final int BUFFER = 2048;
   public static void main (String argv[]) {
      try {
         BufferedOutputStream dest = null;
         FileInputStream fis = new 	   FileInputStream(argv[0]);
         ZipInputStream zis = new 	   ZipInputStream(new BufferedInputStream(fis));
         ZipEntry entry;
         while((entry = zis.getNextEntry()) != null) {
            System.out.println("Extracting: " +entry);
            int count;
            byte data[] = new byte[BUFFER];
            // write the files to the disk
            FileOutputStream fos = new 	      FileOutputStream(entry.getName());
            dest = new               BufferedOutputStream(fos, BUFFER);
            while ((count = zis.read(data, 0, BUFFER))               != -1) {
               dest.write(data, 0, count);
            }
            dest.flush();
            dest.close();
         }
         zis.close();
      } catch(Exception e) {
         e.printStackTrace();
      }
   }}

Publicado en Java

Como crear archivos comprimidos Zip usando las librerías nativas de Java.

// These are the files to include in the ZIP file

    String[] filenames = new String[]{"filename1", "filename2"};

    // Create a buffer for reading the files

    byte[] buf = new byte[1024];

    try {

        // Create the ZIP file

        String outFilename = "outfile.zip";

        ZipOutputStream out = new ZipOutputStream(new FileOutputStream(outFilename));

        // Compress the files

        for (int i=0; i

            FileInputStream in = new FileInputStream(filenames[i]);

            // Add ZIP entry to output stream.

            out.putNextEntry(new ZipEntry(filenames[i]));

            // Transfer bytes from the file to the ZIP file

            int len;

            while ((len = in.read(buf)) > 0) {

                out.write(buf, 0, len);

            }

            // Complete the entry

            out.closeEntry();

            in.close();

        }

        // Complete the ZIP file

        out.close();

    } catch (IOException e) {

    }

Publicado en Java

    Los hilos son lineas de ejecución que queremos que sean ejecutadas concurrentemente para que no bloqueen la linea de ejecución central.

//Proceso principal
Thread hilo = new Thread(){
        public void run ()
        {
            //Ejecuta linea de ejecución concurrente.
        }
    };
    hilo.start();
    //Continuación de la ejecución del proceso principal sin quedarse bloqueado por el hilo.

Publicado en Java