How do I get timezone ids by their milliseconds offset?

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

import java.util.TimeZone;

public class TimeZoneByOffset {
    public static void main(String[] args) {
        // Gets the available IDs according to the given time zone
        // offset in milliseconds.
        int offset = 8 * 60 * 60 * 1000;
        String[] timezones = TimeZone.getAvailableIDs(offset);

        System.out.println("List of available IDs for GMT:+08:00");
        System.out.println("====================================");
        for (String id : timezones) {
            System.out.println(id);
        }
    }
}

Here are the timezone ids in the GMT+8 offset:

List of available IDs for GMT:+08:00
====================================
Asia/Brunei
Asia/Choibalsan
Asia/Chongqing
Asia/Chungking
Asia/Harbin
Asia/Hong_Kong
Asia/Irkutsk
Asia/Kuala_Lumpur
Asia/Kuching
Asia/Macao
Asia/Macau
Asia/Makassar
Asia/Manila
Asia/Shanghai
Asia/Singapore
Asia/Taipei
Asia/Ujung_Pandang
Asia/Ulaanbaatar
Asia/Ulan_Bator
Australia/Perth
Australia/West
CTT
Etc/GMT-8
Hongkong
PRC
Singapore

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
...

How do I convert time between timezone?

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

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public class TimeZoneExample {
    public static void main(String[] args) {
        // Create a calendar object and set it time based on the local
        // time zone
        Calendar localTime = Calendar.getInstance();
        localTime.set(Calendar.HOUR, 17);
        localTime.set(Calendar.MINUTE, 15);
        localTime.set(Calendar.SECOND, 20);

        int hour = localTime.get(Calendar.HOUR);
        int minute = localTime.get(Calendar.MINUTE);
        int second = localTime.get(Calendar.SECOND);

        // Print the local time
        System.out.printf("Local time  : %02d:%02d:%02d\n", hour, minute, second);

        // Create a calendar object for representing a Germany time zone. Then we
        // wet the time of the calendar with the value of the local time
        Calendar germanyTime = new GregorianCalendar(TimeZone.getTimeZone("Germany"));
        germanyTime.setTimeInMillis(localTime.getTimeInMillis());
        hour = germanyTime.get(Calendar.HOUR);
        minute = germanyTime.get(Calendar.MINUTE);
        second = germanyTime.get(Calendar.SECOND);

        // Print the local time in Germany time zone
        System.out.printf("Germany time: %02d:%02d:%02dn", hour, minute, second);
    }
}