How do I count number of weekday between two dates?

By Wayan in Core API, Util Package 0 Comment

The code below helps you find the number of a specified weekday (Monday, Tuesday, Wednesday, etc.) between two dates. The solution we used below is to loop between the two dates and check if the weekday of those dates are equals to the day we want to count.

package org.kodejava.util;

import java.util.Calendar;

public class DaysBetweenDate {
    public static void main(String[] args) {
        Calendar start = Calendar.getInstance();
        start.set(2021, Calendar.OCTOBER, 1);
        Calendar end = Calendar.getInstance();
        end.set(2021, Calendar.OCTOBER, 31);

        System.out.print("Number Monday between " +
                start.getTime() + " and " + end.getTime() + " are: ");

        int numberOfDays = 0;
        while (start.before(end)) {
            if (start.get(Calendar.DAY_OF_WEEK) == Calendar.MONDAY) {
                numberOfDays++;
                start.add(Calendar.DATE, 7);
            } else {
                start.add(Calendar.DATE, 1);
            }
        }

        System.out.println(numberOfDays);
    }
}

The result of our program is:

Number Monday between Fri Oct 01 07:55:06 CST 2021 and Sun Oct 31 07:55:06 CST 2021 are: 4

How do I set Swing Timer initial delay?

By Wayan in Swing 0 Comment

The Swing javax.swing.Timer object fires the action event after the delay time specified in the constructor passed. For some reasons you might want the Timer class fires immediately after it was started.

To achieve this you can set the timer initial delay by calling the setInitialDelay(int initialDelay) method. The example below give you an example how to do it.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class TimerInitialDelayDemo extends JFrame {
    private final JLabel counterLabel = new JLabel();

    private Timer timer = null;

    public TimerInitialDelayDemo() throws HeadlessException {
        initUI();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new TimerInitialDelayDemo().setVisible(true));
    }

    private void initUI() {
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(500, 500);

        Container container = getContentPane();
        container.setLayout(new FlowLayout(FlowLayout.CENTER));
        container.add(counterLabel);

        timer = new Timer(1000, new MyActionListener());

        // Set initial delay of the Timer object. Setting initial delay
        // to zero causes the timer fires the event immediately after
        // it is started.
        timer.setInitialDelay(0);
        timer.start();
    }

    class MyActionListener implements ActionListener {
        private int counter = 10;

        public void actionPerformed(ActionEvent e) {
            counter = counter - 1;
            String text = "<html><font size='14'>" +
                    counter +
                    "</font></head>";
            counterLabel.setText(text);
            if (counter == 0) {
                timer.stop();
            }
        }
    }
}

How do I use Swing Timer class?

By Wayan in Swing 0 Comment

In this example you’ll see how to use java.swing.Timer class to create a text clock program.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.util.Calendar;
import java.text.DateFormat;
import java.text.SimpleDateFormat;

public class TimerDemo extends JFrame {
    public static final DateFormat df = new SimpleDateFormat("hh:mm:ss");

    public TimerDemo() throws HeadlessException {
        initUI();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new TimerDemo().setVisible(true));
    }

    private void initUI() {
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(500, 500);

        Container container = getContentPane();
        container.setLayout(new FlowLayout(FlowLayout.CENTER));

        final JLabel label = new JLabel();
        container.add(label);

        Timer timer = new Timer(1000, e -> {
            Calendar now = Calendar.getInstance();
            String timeText =
                    "<html><font size='10' color='blue'>" +
                            df.format(now.getTime()) +
                            "</font></html>";
            label.setText(timeText);
        });
        timer.start();
    }
}

How do I forward to other page using <jsp:forward>?

By Wayan in Taglib 0 Comment

The <jsp:forward/> tag forward user request to other page. For example, a user request page1.jsp and in this page the server found a <jsp:forward page="page2.jsp"/>. The server immediately stop the processing of page1.jsp and jump to the page2.jsp.

Let see an example of using <jsp:forward/> tag.

page1.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Page 1</title>
</head>
<body>
<strong>This is page 1</strong>

<jsp:forward page="page2.jsp"/>
</body>
</html>

page2.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Page 2</title>
</head>
<body>
<strong>This is page 2</strong>
</body>
</html>

When you try to run the example above by accessing the URL http://localhost:8080/forward/page1.jsp you are going to see the content of page2.jsp instead of page1.jsp. It’s happen because on the server side page1.jsp forward your request to the page2.jsp. But if you look at your browser URL address it will still point to page1.jsp.

Here is the directory structure of our example:

.
├─ pom.xml
└─ src
   └─ main
      └─ webapp
         └─ forward
            └─ page1.jsp
            └─ page2.jsp

Maven Dependencies

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

Maven Central

How do I include other pages using <jsp:include>?

By Wayan in Taglib 0 Comment

The <jsp:include/> tag is use for including another page fragment of a JSP page into another page. This is useful when you have a common page such as header, footer or a menu that applied to many of all of your pages.

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title><jsp:include/> Demo</title>
</head>
<body>
<div id="header">
    <jsp:include page="include/common/header.jsp"/>
</div>

<div id="main">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit,
    sed do eiusmod tempor incididunt ut labore et dolore magna
    aliqua.
</div>

<div id="footer">
    <jsp:include page="include/common/footer.jsp"/>
</div>
</body>
</html>

Here are the page fragment of the header.jsp, footer.jsp and menu.jsp. All of them are placed in the common folder in the same location with the index.jsp file.

header.jsp

<strong><jsp:include/> Demo</strong>
<hr/>
<jsp:include page="menu.jsp"/>

footer.jsp

<hr/>
© 2021 Kode Java Org

menu.jsp

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<a href="<c:url value="/index.jsp"/>">HOME</a>

When you access your page (http://localhost:8080/jsp-include-tag.jsp) from the servlet container such as Apache Tomcat you’ll have a complete display of a page that contains header, menu, content and footer.

Here is the directory structure of our example:

.
.
├─ pom.xml
└─ src
   └─ main
      └─ webapp
         ├─ include
         │  └─ common
         │     ├─ footer.jsp
         │     ├─ header.jsp
         │     └─ menu.jsp
         ├─ jsp-include-tag.jsp
         └─ index.jsp

Maven Dependencies

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

Maven Central