How do I get screen’s display mode information?

By Wayan in AWT, Core API 0 Comment

This example shows graphics devices display mode information such as the display width, height, refresh-rate and bit-depth. This information can be obtained from GraphicsDevice.getDisplayMode() method which return an instance of java.awt.DisplayMode.

We can also get the size of a screen using the following example How do I get my screen size?, but this example can handle only a single screen.

package org.kodejava.awt;

import java.awt.*;

public class GettingScreenDisplayModeInformation {
    public static void main(String[] args) {
        // Get local graphics environment
        GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();

        GraphicsDevice[] devices = env.getScreenDevices();

        int sequence = 1;
        for (GraphicsDevice device : devices) {
            System.out.println("Screen Number [" + (sequence++) + "]");
            System.out.println("Width       : " + device.getDisplayMode().getWidth());
            System.out.println("Height      : " + device.getDisplayMode().getHeight());
            System.out.println("Refresh Rate: " + device.getDisplayMode().getRefreshRate());
            System.out.println("Bit Depth   : " + device.getDisplayMode().getBitDepth());
            System.out.println();
        }
    }
}

An example of the program result:

Screen Number [1]
Width       : 2560
Height      : 1080
Refresh Rate: 60
Bit Depth   : 32

Screen Number [2]
Width       : 2560
Height      : 1080
Refresh Rate: 60
Bit Depth   : 32

How do I get number of available screens?

By Wayan in AWT, Core API 0 Comment

This code shows how to get number of available screen devices on the local machine or local graphics environment. We obtain the number of screens by getting the length of array returned by GraphicsEnvironment.getScreenDevices() method.

This process can produce a HeadlessException to happen if we try to run this code on a machine that doesn’t have a screen device with it.

package org.kodejava.awt;

import java.awt.GraphicsEnvironment;
import java.awt.GraphicsDevice;
import java.awt.HeadlessException;

public class GettingNumberOfScreen {
    public static void main(String[] args) {
        try {
            // Get local graphics environment
            GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();

            // Returns an array of all the screen GraphicsDevice objects.
            GraphicsDevice[] devices = env.getScreenDevices();

            int numberOfScreens = devices.length;
            System.out.println("Number of available screens = " + numberOfScreens);
        } catch (HeadlessException e) {
            // We'll get here if no screen devices was found.
            e.printStackTrace();
        }
    }
}

The output of the code snippet above:

Number of available screens = 2

How do I validate user’s password with PasswordEncryptor?

By Wayan in Jasypt 3 Comments

Every application that you’ll create may require an authentication process. This authentication process will at least contains a process of checking user’s login name and their password. To make the system reliable the password we usually stored the password in an encrypted form.

The BasicPasswordEncryptor which implements the PasswordEncryptor interface provide a BasicPasswordEncryptor.encryptPassword(String password) method for encrypting user’s password. To check if the user’s password is correct we use the BasicPasswordEncryptor.checkPassword(String plainText, String encryptedPassword) method.

package org.kodejava.jasypt;

import org.jasypt.util.password.BasicPasswordEncryptor;
import org.jasypt.util.password.PasswordEncryptor;

public class PasswordEncryptorDemo {
    public static void main(String[] args) {
        // Creates an instance of BasicPasswordEncryptor.
        PasswordEncryptor encryptor = new BasicPasswordEncryptor();

        // Encrypted version of user password.
        String encrypted = encryptor.encryptPassword("secret");
        System.out.println("encrypted = " + encrypted);

        // Compare user's plain text password with the encrypted one to check
        // if they are match.
        if (encryptor.checkPassword("secret", encrypted)) {
            System.out.println("Welcome to Jasypt");
        } else {
            System.out.println("Invalid secret word, access denied!");
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>org.jasypt</groupId>
    <artifactId>jasypt</artifactId>
    <version>1.9.3</version>
</dependency>

Maven Central

How do I create a message digest?

By Wayan in Jasypt

Creating a digest of a string message can be easily done using the general digester class Digester. First we need to get an instance of Digester, we call the class constructor and pass SHA-1 as the algorithm. After having a Digester instance we create the message digest by executing or calling the Digester.digest(byte[] binary) method of this class.

package org.kodejava.jasypt;

import org.jasypt.util.digest.Digester;

import java.util.Arrays;

public class DigesterDemo {
    public static void main(String[] args) {
        // Creates a new instance of Digester, using the SHA-1 algorithm.
        Digester digester = new Digester("SHA-1");

        byte[] message = "Hello World from Jasypt".getBytes();

        // Creates a digest from an array of byte message.
        byte[] digest = digester.digest(message);

        System.out.println("Digest = " + new String(digest));
        System.out.println("Digest = " + Arrays.toString(digest));
    }
}

Maven Dependencies

<dependency>
    <groupId>org.jasypt</groupId>
    <artifactId>jasypt</artifactId>
    <version>1.9.3</version>
</dependency>

Maven Central

How do I encrypt or decrypt bytes information using StandardPBEByteEncryptor?

By Wayan in Jasypt 0 Comment

This code demonstrate how to use the StandardPBEByteEncryptor class to encrypt and decrypt bytes information.

package org.kodejava.jasypt;

import org.jasypt.encryption.pbe.StandardPBEByteEncryptor;

import java.util.Arrays;

public class ByteEncryptorDemo {
    public static void main(String[] args) {
        String text = "The quick brown fox jumps over the lazy dog";
        System.out.println("Text      = " + Arrays.toString(text.getBytes()));

        StandardPBEByteEncryptor encryptor = new StandardPBEByteEncryptor();
        encryptor.setAlgorithm("PBEWithMD5AndDES");
        encryptor.setPassword("HelloWorld");

        byte[] encrypted = encryptor.encrypt(text.getBytes());
        System.out.println("Encrypted = " + Arrays.toString(encrypted));

        byte[] original = encryptor.decrypt(encrypted);
        System.out.println("Original  = " + Arrays.toString(original));
    }
}

The results of our code are:

Text      = [84, 104, 101, 32, 113, 117, 105, 99, 107, 32, 98, 114, 111, 119, 110, 32, 102, 111, 120, 32, 106, 117, 109, 112, 115, 32, 111, 118, 101, 114, 32, 116, 104, 101, 32, 108, 97, 122, 121, 32, 100, 111, 103]
Encrypted = [64, -99, -51, -21, -2, -6, -1, 76, -46, 87, 119, 62, -83, -74, 30, -90, 0, -97, 92, 0, 116, 32, -97, 67, -121, 57, -116, -11, 52, -73, 0, -104, -85, -109, -28, 106, 100, -76, -75, 55, -12, 49, 16, 65, -37, 88, 78, -68, 39, 14, 96, -22, 56, 63, -26, 18]
Original  = [84, 104, 101, 32, 113, 117, 105, 99, 107, 32, 98, 114, 111, 119, 110, 32, 102, 111, 120, 32, 106, 117, 109, 112, 115, 32, 111, 118, 101, 114, 32, 116, 104, 101, 32, 108, 97, 122, 121, 32, 100, 111, 103]

Maven Dependencies

<dependency>
    <groupId>org.jasypt</groupId>
    <artifactId>jasypt</artifactId>
    <version>1.9.3</version>
</dependency>

Maven Central

How do I use BasicTextEncryptor for encrypting and decrypting string information?

By Wayan in Jasypt 1 Comment

This example is showing you how to use the Jasypt API to write a simple code to do string encryption and decryption. In this example we are going to use the BasicTextEncryptor class which use the PBEWithMD5AndDES algorithm. This class is an implementation of the TextEncryoptor interface.

You can download the library from their website, it’s already included with the dependency libraries required by Jasypt such as the commons-codec and commons-lang.

package org.kodejava.jasypt;

import org.jasypt.util.text.BasicTextEncryptor;

public class TextEncryptorDemo {
    public static void main(String[] args) {
        String text = "The quick brown fox jumps over the lazy dog";
        System.out.println("Text      = " + text);

        BasicTextEncryptor bte = new BasicTextEncryptor();
        bte.setPassword("HelloWorld");

        String encrypted = bte.encrypt(text);
        System.out.println("Encrypted = " + encrypted);

        String original = bte.decrypt(encrypted);
        System.out.println("Original  = " + original);
    }
}

The result produced by the code above:

Text      = The quick brown fox jumps over the lazy dog
Encrypted = kYXn3rL/YChh9EraGYh3cyuRxLo+dKocd+W33yW53TfgQecTpLRcIt5AH974d0YFDcFFXUTfNAk=
Original  = The quick brown fox jumps over the lazy dog

Maven Dependencies

<dependency>
    <groupId>org.jasypt</groupId>
    <artifactId>jasypt</artifactId>
    <version>1.9.3</version>
</dependency>

Maven Central

How do I format a message that contains number information?

By Wayan in Core API, Text Package 0 Comment

This example show you how to use java.text.MessageFormat class to format a message that contains numbers.

package org.kodejava.text;

import java.text.MessageFormat;
import java.util.Locale;

public class MessageFormatNumber {
    public static void main(String[] args) {

        // Set the Locale for the MessageFormat.
        Locale.setDefault(Locale.US);

        // Use the default formatting for number.
        String message = MessageFormat.format("This is a {0} and {1} numbers",
                10, 75);
        System.out.println(message);

        // This line has the same format as above.
        message = MessageFormat.format("This is a {0,number} and {1,number} " +
                "numbers", 10, 75);
        System.out.println(message);

        // Format a number with 2 decimal digits.
        message = MessageFormat.format("This is a formatted {0, number,#.##} " +
                "and {1, number,#.##} numbers", 25.7575, 75.2525);
        System.out.println(message);

        // Format a number as currency.
        message = MessageFormat.format("This is a formatted currency " +
                        "{0,number,currency} and {1,number,currency} numbers",
                25.7575, 25.7575);
        System.out.println(message);

        // Format numbers in percentage.
        message = MessageFormat.format("This is a formatted percentage " +
                "{0,number,percent} and {1,number,percent} numbers", 0.10, 0.75);
        System.out.println(message);
    }
}

The result of the program are the following lines:

This is a 10 and 75 numbers
This is a 10 and 75 numbers
This is a formatted 25.76 and 75.25 numbers
This is a formatted currency $25.76 and $25.76 numbers
This is a formatted percentage 10% and 75% numbers

How do I format a message that contains time information?

By Wayan in Core API, Text Package 0 Comment

Here we demonstrate how to use the java.text.MessageFormat class to format a message contains time information.

package org.kodejava.text;

import java.util.Date;
import java.util.Calendar;
import java.util.Locale;
import java.text.MessageFormat;

public class MessageFormatTime {
    public static void main(String[] args) {
        Date today = new Date();
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.HOUR, 7);

        Date next7Hours = calendar.getTime();

        // We want the message to be is Locale.US
        Locale.setDefault(Locale.US);

        // Format a time including date information.
        String message = MessageFormat.format("Now is {0} and the next " +
                "7 hours is {1}", today, next7Hours);
        System.out.println(message);

        // Format a time and display only the time portion
        message = MessageFormat.format("Now is {0, time} and the next " +
                "7 hours is {1, time}", today, next7Hours);
        System.out.println(message);

        // Format a time using a short format (e.g. HH:mm am/pm)
        message = MessageFormat.format("Now is {0, time, short} and " +
                "the next 7 hours is {1, time, short}", today, next7Hours);
        System.out.println(message);

        // Format a time using a medium format (eg. HH:mm:ss am/pm).
        message = MessageFormat.format("Now is {0, time, medium} and " +
                "the next 7 hours is {1, time, medium}", today, next7Hours);
        System.out.println(message);

        // Format a time using a long format (e.g. HH:mm:ss am/pm TIMEZONE).
        message = MessageFormat.format("Now is {0, time, long} and the " +
                "next 7 hours is {1, time, long}", today, next7Hours);
        System.out.println(message);

        // Format a time using a full format (e.g. HH:mm:ss am/pm TIMEZONE).
        message = MessageFormat.format("Now is {0, time, full} and the " +
                "next 7 hours is {1, time, full}", today, next7Hours);
        System.out.println(message);

        // Format a time using a custom pattern.
        message = MessageFormat.format("Now is {0, time, HH:mm:ss.sss} " +
                "and the next 7 hours is {1, time, HH:mm:ss.sss}", today, next7Hours);
        System.out.println(message);
    }
}

The above program produces:

Now is 10/8/21, 9:38 PM and the next 7 hours is 10/9/21, 4:38 AM
Now is 9:38:10 PM and the next 7 hours is 4:38:10 AM
Now is 9:38 PM and the next 7 hours is 4:38 AM
Now is 9:38:10 PM and the next 7 hours is 4:38:10 AM
Now is 9:38:10 PM CST and the next 7 hours is 4:38:10 AM CST
Now is 9:38:10 PM China Standard Time and the next 7 hours is 4:38:10 AM China Standard Time
Now is  21:38:10.010 and the next 7 hours is  04:38:10.010

How do I format a message that contains date information?

By Wayan in Core API, Text Package 0 Comment

This example demonstrate how you can use the java.text.MessageFormat class to format a message with a date information in it.

package org.kodejava.text;

import java.util.Date;
import java.util.Calendar;
import java.util.Locale;
import java.text.MessageFormat;

public class MessageFormatDate {
    public static void main(String[] args) {
        Date today = new Date();
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, 7);

        Date nextWeek = calendar.getTime();

        // We want the message to be is Locale.US
        Locale.setDefault(Locale.US);

        // Format a date, the time value is included
        String message = MessageFormat.format("Today is {0} and next " +
                "week is {1}", today, nextWeek);
        System.out.println(message);

        // Format a date and display only the date portion
        message = MessageFormat.format("Today is {0,date} and next " +
                "week is {1,date}", today, nextWeek);
        System.out.println(message);

        // Format a date using a short format (e.g. dd/MM/yyyy)
        message = MessageFormat.format("Today is {0,date,short} and " +
                "next week is {1,date,short}", today, nextWeek);
        System.out.println(message);

        // Format a date using a medium format, it displays the month long-name,
        // but using a two digit date and year.
        message = MessageFormat.format("Today is {0,date,medium} and " +
                "next week is {1,date,medium}", today, nextWeek);
        System.out.println(message);

        // Format a date using a long format, two digit for date, a long month
        // name and a four digit year.
        message = MessageFormat.format("Today is {0,date,long} and " +
                "next week is {1,date,long}", today, nextWeek);
        System.out.println(message);

        // Format a date using a full format, the same as above plus a full day
        // name.
        message = MessageFormat.format("Today is {0,date,full} and " +
                "next week is {1,date,full}", today, nextWeek);
        System.out.println(message);

        // Format a date using a custom pattern.
        message = MessageFormat.format("Today is {0,date,dd-MM-yyyy} and " +
                "next week is {1,date,dd-MM-yyyy}", today, nextWeek);
        System.out.println(message);
    }
}

The above program produces:

Today is 10/8/21, 9:35 PM and next week is 10/15/21, 9:35 PM
Today is Oct 8, 2021 and next week is Oct 15, 2021
Today is 10/8/21 and next week is 10/15/21
Today is Oct 8, 2021 and next week is Oct 15, 2021
Today is October 8, 2021 and next week is October 15, 2021
Today is Friday, October 8, 2021 and next week is Friday, October 15, 2021
Today is 08-10-2021 and next week is 15-10-2021

How do I check if a cell contains a date value?

By Wayan in Apache POI 5 Comments

The code below check if the first cell of an Excel file contains a date value. In Excel the cell type for date is returned as HSSFCell.CELL_TYPE_NUMERIC, to make sure if it contains a date we can use a utility method DateUtil.isCellDateFormatted(Cell cell), this method will check if the cell value is a valid date.

package org.kodejava.poi;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.DateUtil;

import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class DateCellType {
    public static void main(String[] args) throws Exception {
        String filename = "datecelltype.xls";

        try (FileInputStream fis = new FileInputStream(filename)) {
            HSSFWorkbook workbook = new HSSFWorkbook(fis);
            HSSFSheet sheet = workbook.getSheetAt(0);

            // Read a cell the first cell on the sheet.
            HSSFCell cell = sheet.getRow(0).getCell(0);
            if (cell.getCellType() == CellType.NUMERIC) {
                System.out.println("Cell type for date data type is numeric.");
            }

            // Using HSSFDateUtil to check if a cell contains a date.
            if (DateUtil.isCellDateFormatted(cell)) {
                System.out.println("The cell contains a date value: "
                        + cell.getDateCellValue());
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

The example result of the code snippet:

Cell type for date data type is numeric.
The cell contains a date value: Fri Oct 08 00:00:00 CST 2021

Maven Dependencies

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>5.2.5</version>
</dependency>

Maven Central