How do I detect non-ASCII characters in string?

By Wayan in Core API, IO 0 Comment

The code below detect if a given string has a non ASCII characters in it. We use the CharsetDecoder class from the java.nio package to decode string to be a valid US-ASCII charset.

package org.kodejava.io;

import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharacterCodingException;
import java.nio.CharBuffer;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;

public class NonAsciiValidation {
    public static void main(String[] args) {
        // This string contains a non ASCII character which will produce exception
        // in this program. While the second string has a valid ASCII only characters.
        byte[] invalidBytes = "Copyright © 2021 Kode Java Org".getBytes();
        byte[] validBytes = "Copyright (c) 2021 Kode Java Org".getBytes();

        // Returns a charset object for the named charset.
        CharsetDecoder decoder = StandardCharsets.US_ASCII.newDecoder();
        try {
            CharBuffer buffer = decoder.decode(ByteBuffer.wrap(validBytes));
            System.out.println(Arrays.toString(buffer.array()));

            buffer = decoder.decode(ByteBuffer.wrap(invalidBytes));
            System.out.println(Arrays.toString(buffer.array()));
        } catch (CharacterCodingException e) {
            System.err.println("The information contains a non ASCII character(s).");
            e.printStackTrace();
        }
    }
}

Below is the result of the program:

[C, o, p, y, r, i, g, h, t,  , (, c, ),  , 2, 0, 2, 1,  , K, o, d, e,  , J, a, v, a,  , O, r, g]
The information contains a non ASCII character(s).
java.nio.charset.MalformedInputException: Input length = 1
    at java.base/java.nio.charset.CoderResult.throwException(CoderResult.java:274)
    at java.base/java.nio.charset.CharsetDecoder.decode(CharsetDecoder.java:820)
    at org.kodejava.io.NonAsciiValidation.main(NonAsciiValidation.java:23)

How do I create temporary file?

By Wayan in Core API, IO 0 Comment

A temporary file can be created by using java.io.File.createTempFile() method. It accepts the prefix, suffix and the path where the file will be stored. When no path is specified it will use the platform default temporary folder.

The name of the temporary file will be in the form of prefix plus five or more random characters plus the suffix. When the suffix is null a default .tmp will be used for suffix.

package org.kodejava.io;

import java.io.File;
import java.io.BufferedWriter;
import java.io.FileWriter;

public class TemporaryFileDemo {
    public static void main(String[] args) throws Exception {
        // Create a temporary file userlist.txt in the default platform
        // temporary folder / directory. We can get the platform temporary
        // folder using System.getProperty("java.io.tmpdir")
        File user = File.createTempFile("userlist", ".txt");

        // Delete the file when the virtual machine is terminated.
        user.deleteOnExit();

        // Create a temporary file data.txt in the user specified folder.
        File data = File.createTempFile("data", ".txt", new File("F:/Temp/Data"));
        data.deleteOnExit();

        // Write data into temporary file
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(data))) {
            writer.write("750101,2008-01-01,BLUE,CAR");
            writer.write("750102,2008-09-06,RED,CAR");
            writer.write("750103,2008-05-01,GREEN,CAR");
            writer.write("750104,2008-06-08,YELLOW,CAR");
        }
    }
}

How do I add hours, minutes or seconds to a date?

By Wayan in Core API, Util Package 0 Comment

This example shows you how to add or subtract hours, minutes or seconds to a date using the java.util.Calendar object.

package org.kodejava.util;

import java.util.Calendar;

public class DateAddSubtract {
    public static void main(String[] args) {
        // Gets a calendar using the default time zone and locale. The
        // Calendar returned is based on the current time in the default
        // time zone with the default locale.
        Calendar calendar = Calendar.getInstance();
        System.out.println("Original = " + calendar.getTime());

        // Subtract 2 hour from the current time
        calendar.add(Calendar.HOUR, -2);

        // Add 30 minutes to the calendar time
        calendar.add(Calendar.MINUTE, 30);

        // Add 300 seconds to the calendar time
        calendar.add(Calendar.SECOND, 300);
        System.out.println("Updated  = " + calendar.getTime());
    }
}

The output of the code snippet:

Original = Wed Oct 06 19:47:53 CST 2021
Updated  = Wed Oct 06 18:22:53 CST 2021

How do I format date using a locale based format?

By Wayan in Core API, Text Package 0 Comment

The code below demonstrate how to format date information for a specific locale. In the example utilize the java.text.SimpleDateFormat class.

package org.kodejava.text;

import java.util.Locale;
import java.util.Date;
import java.text.SimpleDateFormat;

public class FormatDateLocale {
    public static void main(String[] args) {
        // Defines an array of Locale we are going to use for
        // formatting date information.
        Locale[] locales = new Locale[] {
            Locale.JAPAN,
            Locale.CHINA,
            Locale.KOREA,
            Locale.TAIWAN,
            Locale.ITALY,
            Locale.FRANCE,
            Locale.GERMAN
        };

        // Get an instance of current date time
        Date today = new Date();

        // Iterates the entire Locale defined above and create a long
        // formatted date using the SimpleDateFormat.getDateInstance()
        // with the format, the Locale and the date information.
        for (Locale locale : locales) {
            System.out.printf("Date format in %s = %s%n",
                locale.getDisplayName(), SimpleDateFormat.getDateInstance(
                    SimpleDateFormat.LONG, locale).format(today));
        }
    }
}

The result of our code are:

Date format in Japanese (Japan) = 2021年10月6日
Date format in Chinese (China) = 2021年10月6日
Date format in Korean (South Korea) = 2021년 10월 6일
Date format in Chinese (Taiwan) = 2021年10月6日
Date format in Italian (Italy) = 6 ottobre 2021
Date format in French (France) = 6 octobre 2021
Date format in German = 6. Oktober 2021

How do I customize JButton icons?

By Wayan in Swing 0 Comment

The example below shows you how we can customize the icon for JButton Swing components.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class JButtonCustomIcon extends JFrame {
    public JButtonCustomIcon() throws HeadlessException {
        initialize();
    }

    private void initialize() {
        setSize(500, 500);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLayout(new FlowLayout(FlowLayout.LEFT));

        JButton button = new JButton("Press Me!");

        // Below is how we can set various icons for the JButton swing
        // component. There are the default icon, selected, disabled, pressed
        // and rollover icons.
        button.setIcon(new ImageIcon("default.png"));
        button.setSelectedIcon(new ImageIcon("selected.png"));
        button.setDisabledIcon(new ImageIcon("disabled.png"));
        button.setDisabledSelectedIcon(new ImageIcon("disabledSelected.png"));
        button.setPressedIcon(new ImageIcon("pressed.png"));
        button.setRolloverIcon(new ImageIcon("rollover.png"));
        button.setRolloverSelectedIcon(new ImageIcon("rolloverSelected.png"));

        getContentPane().add(button);
    }

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