How do I copy file?

By Wayan in Core API, IO 0 Comment

This example demonstrates how to copy file using the Java IO library. Here we will use the java.io.FileInputStream and it’s tandem the java.io.FileOutputStream class.

package org.kodejava.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileCopyDemo {
    public static void main(String[] args) {
        // Create an instance of source and destination files
        File source = new File("source.pdf");
        File destination = new File("target.pdf");

        try (FileInputStream fis = new FileInputStream(source);
             FileOutputStream fos = new FileOutputStream(destination)) {
            // Define the size of our buffer for buffering file data
            byte[] buffer = new byte[4096];
            int read;
            while ((read = fis.read(buffer)) != -1) {
                fos.write(buffer, 0, read);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

How do I clear system property?

By Wayan in Core API, Lang Package 0 Comment

The System.clearProperty(String key) method enables you to remove a system property. The key must not be an empty string or a null value because it will cause the method to throw an IllegalArgumentException or a NullPointerException.

It will also check if a SecurityManager exists and if you don’t have a write permission to the system property a SecurityException is going to be thrown.

package org.kodejava.lang;

public class ClearProperty {
    public static void main(String[] args) {
        String key = "user.dir";
        System.out.println(key + " = " + System.getProperty(key));

        // The System.clearProperty() method available since Java 1.5
        System.clearProperty(key);
        System.out.println(key + " = " + System.getProperty(key));
    }
}

The code snippet above give us the following output:

user.dir = F:\Wayan\Kodejava\kodejava-example
user.dir = null

How do I handle JFrame window events?

By Wayan in Swing 0 Comment

This example show you how to handle JFrame window events such as windowOpened, windowClosing, windowClosed, etc. For handling these events we need to add a WindowListener listener to the JFrame instance. Here we use the WindowAdapter abstract class and implement the method which event we want to handle.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class WindowListenerDemo extends JFrame {
    public WindowListenerDemo() {
        initializeComponent();
    }

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

    private void initializeComponent() {
        setSize(500, 500);
        setTitle("Window Listener");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        this.addWindowListener(new WindowAdapter() {
            // Invoked when a window has been opened.
            public void windowOpened(WindowEvent e) {
                System.out.println("Window Opened Event");
            }

            // Invoked when a window is in the process of being closed.
            // The close operation can be overridden at this point.
            public void windowClosing(WindowEvent e) {
                System.out.println("Window Closing Event");
            }

            // Invoked when a window has been closed.
            public void windowClosed(WindowEvent e) {
                System.out.println("Window Close Event");
            }

            // Invoked when a window is iconified.
            public void windowIconified(WindowEvent e) {
                System.out.println("Window Iconified Event");
            }

            // Invoked when a window is de-iconified.
            public void windowDeiconified(WindowEvent e) {
                System.out.println("Window Deiconified Event");
            }

            // Invoked when a window is activated.
            public void windowActivated(WindowEvent e) {
                System.out.println("Window Activated Event");
            }

            // Invoked when a window is de-activated.
            public void windowDeactivated(WindowEvent e) {
                System.out.println("Window Deactivated Event");
            }

            // Invoked when a window state is changed.
            public void windowStateChanged(WindowEvent e) {
                System.out.println("Window State Changed Event");
            }

            // Invoked when the Window is set to be the focused Window, which means
            // that the Window, or one of its sub components, will receive keyboard
            // events.
            public void windowGainedFocus(WindowEvent e) {
                System.out.println("Window Gained Focus Event");
            }

            // Invoked when the Window is no longer the focused Window, which means
            // that keyboard events will no longer be delivered to the Window or any of
            // its sub components.
            public void windowLostFocus(WindowEvent e) {
                System.out.println("Window Lost Focus Event");
            }
        });
    }
}

How do I get file separator symbol?

By Wayan in Core API, Lang Package 0 Comment

Creating a program to be run on more than one platform such as Windows and Linux our program need to understand the difference between both platform. The simplest thing for instance is the file separator. Windows use "\" (backslash) while Linux use "/" (forward slash).

To avoid manual checking for the operating system we can get the file separator symbol from the system property using the file.separator key.

package org.kodejava.lang;

public class FileSeparatorExample {
    public static void main(String[] args) {
        // file.separator system property return the correct file 
        // separator for each different platform (Windows = \), 
        // (Linux = /)
        String dataFolder = System.getProperty("user.dir") +
                System.getProperty("file.separator") + "data";

        System.out.println("Data Folder = " + dataFolder);
    }
}

How do I change date formatting symbols?

By Wayan in Core API, Text Package 0 Comment

This example shows how we can change the date formatting symbols. In this example we change the month names and short month names and also the weekday names and short weekday names.

Other than these two items we can also change other symbols such as the Era name and AM-PM string.

package org.kodejava.text;

import java.text.SimpleDateFormat;
import java.text.DateFormat;
import java.text.DateFormatSymbols;
import java.util.Date;

public class DateFormatSymbolsExample {
    public static void main(String[] args) {
        // Defining a new Date Format Symbols, the following are month and day
        // names in Bahasa Indonesia.
        String[] newMonths = {"JANUARI", "FEBRUARI", "MARET", "APRIL", "MEI",
                "JUNI", "JULI", "AGUSTUS", "SEPTEMBER", "OKTOBER", "NOVEMBER",
                "DESEMBER"};
        String[] newShortMonths = {"JAN", "FEB", "MAR", "APR", "MEI", "JUN",
                "JUL", "AGU", "SEP", "OKT", "NOV", "DES"};
        String[] newWeekdays = {"", "MINGGU", "SENIN", "SELASA", "RABU", "KAMIS",
                "JUMAT", "SABTU"};
        String[] shortWeekdays = {"", "MIN", "SEN", "SEL", "RAB", "KAM", "JUM",
                "SAB"};

        DateFormatSymbols symbols = new DateFormatSymbols();
        symbols.setMonths(newMonths);
        symbols.setShortMonths(newShortMonths);
        symbols.setWeekdays(newWeekdays);
        symbols.setShortWeekdays(shortWeekdays);

        DateFormat format = new SimpleDateFormat("dd MMMM yyyy", symbols);
        System.out.println(format.format(new Date()));

        format = new SimpleDateFormat("dd MMM yyyy", symbols);
        System.out.println(format.format(new Date()));

        format = new SimpleDateFormat("EEEE, dd MMM yyyy", symbols);
        System.out.println(format.format(new Date()));

        format = new SimpleDateFormat("E, dd MMM yyyy", symbols);
        System.out.println(format.format(new Date()));
    }
}

The result of the code snippet above is:

02 OKTOBER 2021
02 OKT 2021
SABTU, 02 OKT 2021
SAB, 02 OKT 2021