How do I remove substring from StringBuilder?

By I Wayan Saryada in Core API, Lang Package 0 Comment

This example demonstrate you how to use the StringBuilder delete(int start, int end) and deleteCharAt(int index) to remove a substring or a single character from a StringBuilder.

package org.kodejava.lang;

public class StringBuilderDelete {
    public static void main(String[] args) {
        StringBuilder lipsum = new StringBuilder("Lorem ipsum dolor sit " +
                "amet, consectetur adipisicing elit.");
        System.out.println("lipsum = " + lipsum);

        // We'll remove a substring from this StringBuilder starting from
        // the first character to the 28th character.
        lipsum.delete(0, 28);
        System.out.println("lipsum = " + lipsum);

        // Removes a char from the StringBuilder. In the example below we
        // remove the last character.
        lipsum.deleteCharAt(lipsum.length() - 1);
        System.out.println("lipsum = " + lipsum);
    }
}

The result of the code snippet above:

lipsum = Lorem ipsum dolor sit amet, consectetur adipisicing elit.
lipsum = consectetur adipisicing elit.
lipsum = consectetur adipisicing elit

How do I convert time between timezone?

By I Wayan Saryada 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);
    }
}

How do I set default Locale?

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

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Random;

public class DefaultLocaleExample {
    public static void main(String[] args) {
        // Use Random class to generate some random number
        Random random = new Random();

        // We use the system default locale to format a number and a date.
        NumberFormat formatter = new DecimalFormat();
        Locale locale = Locale.getDefault();
        System.out.println("Default Locale = " + locale);
        System.out.println("Number         = " + formatter.format(random.nextDouble()));
        System.out.println("Date           = " + new SimpleDateFormat().format(new Date()));

        // We change the default locale to Locale.ITALY by setting it through 
        // the Locale.setDefault() method, and then we format another number
        // and date using a new locale. This change will affect all the class 
        // that aware to the Locale, such as the NumberFormat class.
        Locale.setDefault(Locale.ITALY);
        NumberFormat newFormatter = new DecimalFormat();
        System.out.println("New Locale     = " + Locale.getDefault());
        System.out.println("Number         = " + newFormatter.format(random.nextDouble()));
        System.out.println("Date           = " + new SimpleDateFormat().format(new Date()));
    }
}

The result of the code snippet above are:

Default Locale = en_US
Number         = 0.557
Date           = 9/26/21, 12:05 PM
New Locale     = it_IT
Number         = 0,217
Date           = 26/09/21, 12:05

How do I get response header from HTTP request?

By I Wayan Saryada in Core API, Networking 0 Comment 
package org.kodejava.net;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

public class HttpResponseHeaderDemo {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://kodejava.org/index.php");
            URLConnection connection = url.openConnection();

            Map<String, List<String>> responseMap = connection.getHeaderFields();
            for (String key : responseMap.keySet()) {
                System.out.print(key + " = ");

                List<String> values = responseMap.get(key);
                for (String value : values) {
                    System.out.print(value + ", ");
                }
                System.out.println();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

The result produced by the code above are:

null = HTTP/1.1 200 OK, 
Referrer-Policy = no-referrer-when-downgrade, 
Content-Length = 147566, 
Content-Type = text/html; charset=UTF-8, 
Connection = keep-alive, 
Date = Sun, 26 Sep 2021 03:59:06 GMT, 
Accept-Ranges = bytes, 
Vary = Accept-Encoding, Accept-Encoding, 
Link = <https://wp.me/8avgG>; rel=shortlink, <https://kodejava.org/wp-json/>; rel="https://api.w.org/",

How do I create a URL object?

By I Wayan Saryada in Core API, Networking 0 Comment 
package org.kodejava.net;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class URLDemo {
    public static void main(String[] args) {
        try {
            // Creating a url object by specifying each parameter separately, including
            // the protocol, hostname, port number, and the page name
            URL url = new URL("https", "kodejava.org", 443, "/index.php");

            // We can also specify the address in a single line
            url = new URL("https://kodejava.org:443/index.php");

            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(url.openStream(), StandardCharsets.UTF_8));

            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }

            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}