How do I compare two dates?

By Wayan in Core API, Util Package 0 Comment

In this example you’ll see the utilization of SimpleDateFormat class for comparing two dates for equality. We convert the date object into string using the DateFormat instance and then compare it using String.equals() method.

package org.kodejava.util;

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

public class ComparingDate {
    public static void main(String[] args) {
        // Create a SimpleDateFormat instance with dd/MM/yyyy format
        DateFormat df = new SimpleDateFormat("dd/MM/yyyy");

        // Get the current date
        Date today = new Date();

        // Create an instance of calendar that represents a new year date
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.DATE, 1);
        calendar.set(Calendar.MONTH, Calendar.JANUARY);
        calendar.set(Calendar.YEAR, 2021);

        String newYear = df.format(calendar.getTime());
        String now = df.format(today);

        // Using the string equals method we can compare the date.
        if (now.equals(newYear)) {
            System.out.println("Happy New Year!");
        } else {
            System.out.println("Have a nice day!");
        }
    }
}

How do I convert ResourceBundle to Properties?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.*;

public class ResourceBundleToProperties {
    public static void main(String[] args) {
        // Load resource bundle Messages_en_GB.properties from the classpath.
        ResourceBundle resource = ResourceBundle.getBundle("Messages", Locale.UK);

        // Call the convertResourceBundleToProperties method to convert the resource
        // bundle into a Properties object.
        Properties properties = convertResourceBundleToProperties(resource);

        // Print the entire contents of the Properties.
        Enumeration<Object> keys = properties.keys();
        while (keys.hasMoreElements()) {
            String key = (String) keys.nextElement();
            String value = (String) properties.get(key);
            System.out.println(key + " = " + value);
        }
    }

    /**
     * Convert ResourceBundle into a Properties object.
     *
     * @param resource a resource bundle to convert.
     * @return Properties a properties version of the resource bundle.
     */
    private static Properties convertResourceBundleToProperties(ResourceBundle resource) {
        Properties properties = new Properties();
        Enumeration<String> keys = resource.getKeys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            properties.put(key, resource.getString(key));
        }
        return properties;
    }
}

How do I convert ResourceBundle to Map?

By Wayan in Core API, Util Package 1 Comment

The following code snippet will convert a resource bundle into a map object, a key-value mapping. It will read from a file called Messages_en_GB.properties which corresponding to the Locale.UK. For example the file contain the following string. This file should be placed under the resources directory.

welcome.message = Hello World!

package org.kodejava.util;

import java.util.*;

public class ResourceBundleToMap {
    public static void main(String[] args) {
        // Load resource bundle Messages_en_GB.properties from the classpath.
        ResourceBundle resource = ResourceBundle.getBundle("Messages", Locale.UK);

        // Call the convertResourceBundleTopMap method to convert the resource
        // bundle into a Map object.
        Map<String, String> map = convertResourceBundleToMap(resource);

        // Print the entire contents of the Map.
        for (String key : map.keySet()) {
            String value = map.get(key);
            System.out.println(key + " = " + value);
        }
    }

    /**
     * Convert ResourceBundle into a Map object.
     *
     * @param resource a resource bundle to convert.
     * @return Map a map version of the resource bundle.
     */
    private static Map<String, String> convertResourceBundleToMap(ResourceBundle resource) {
        Map<String, String> map = new HashMap<>();
        Enumeration<String> keys = resource.getKeys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            map.put(key, resource.getString(key));
        }
        return map;
    }
}

How do I convert LinkedList to array?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.LinkedList;
import java.util.List;

public class LinkedListToArray {
    public static void main(String[] args) {
        List<String> list = new LinkedList<>();
        list.add("Blue");
        list.add("Green");
        list.add("Purple");
        list.add("Orange");

        // Converting LinkedList to array can be done by calling the toArray()
        // method of the List;
        String[] colors = new String[list.size()];
        list.toArray(colors);

        for (String color : colors) {
            System.out.println("color = " + color);
        }
    }
}

How do I get all available timezones?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.TimeZone;

public class TimezonesExample {
    public static void main(String[] args) {
        String[] availableTimezones = TimeZone.getAvailableIDs();

        for (String timezone : availableTimezones) {
            System.out.println("Timezone ID = " + timezone);
        }
    }
}

Some examples of the returned timezones ids are:

Timezone ID = Etc/GMT+12
Timezone ID = Etc/GMT+11
Timezone ID = MIT
Timezone ID = Pacific/Apia
Timezone ID = Pacific/Midway
Timezone ID = Pacific/Niue
Timezone ID = Pacific/Pago_Pago
Timezone ID = Pacific/Samoa
Timezone ID = US/Samoa
...