How do I change DecimalFormat pattern?

By Wayan in Core API, Text Package 0 Comment

To change the pattern use by the DecimalFormat when formatting a number we can use the DecimalFormat.applyPattern() method call. In this example we use three different patterns to format the given input number. The pattern determines what the formatted number looks like.

package org.kodejava.text;

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;

public class FormatterPattern {
    public static void main(String[] args) {
        String[] patterns = {"###,###,###.##", "000000000.00", "$###,###.##"};

        double before = 1234567.899;

        // To obtain a NumberFormat for a specific locale,
        // including the default locale, call one of NumberFormat's
        // factory methods, such as getNumberInstance(). Then cast
        // it into a DecimalFormat.
        DecimalFormat format =
                (DecimalFormat) NumberFormat.getNumberInstance(Locale.UK);
        for (String pattern : patterns) {
            // Apply the given pattern to this Format object
            format.applyPattern(pattern);

            // Gets the formatted value
            String after = format.format(before);

            System.out.printf("Input: %s, Pattern: %s, Output: %s%n",
                    before, pattern, after);
        }
    }
}

The output of the program shown below:

Input: 1234567.899, Pattern: ###,###,###.##, Output: 1,234,567.9
Input: 1234567.899, Pattern: 000000000.00, Output: 001234567.90
Input: 1234567.899, Pattern: $###,###.##, Output: $1,234,567.9

How do I format number as percentage string?

By Wayan in Core API, Text Package 0 Comment

The NumberFormat.getPercentInstance() method returns a percentage format for the specified locale. In this example we will format the number as percentage using the Locale.US locale.

package org.kodejava.text;

import java.text.NumberFormat;
import java.util.Locale;

public class LocalePercentageFormat {
    public static void main(String[] args) {
        // Format percentage for Locale.US locale with this formatter,
        // a decimal fraction such as 0.75 is displayed as 75%
        double number = 0.25;
        NumberFormat format = NumberFormat.getPercentInstance(Locale.US);
        String percentage = format.format(number);
        System.out.println(number + " in percentage = " + percentage);
    }
}

The following line is the output of the program:

0.25 in percentage = 25%

How do I format a number as currency string?

By Wayan in Core API, Text Package 6 Comments

Creating a financial application requires you to format number as a currency. It should include the correct thousand separator, decimal separator and the currency symbol. For this purpose you can use the NumberFormat.getCurrencyInstance() method and pass the correct Locale to get the currency format that you want.

package org.kodejava.text;

import java.text.NumberFormat;
import java.util.Locale;

public class LocaleCurrencyFormat {
    public static void main(String[] args) {
        Double number = 1500D;

        // Format currency for Canada locale in Canada locale, 
        // the decimal point symbol is a comma and currency
        // symbol is $.
        NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CANADA);
        String currency = format.format(number);
        System.out.println("Currency in Canada : " + currency);

        // Format currency for Germany locale in German locale,
        // the decimal point symbol is a dot and currency symbol
        // is €.
        format = NumberFormat.getCurrencyInstance(Locale.GERMANY);
        currency = format.format(number);
        System.out.println("Currency in Germany: " + currency);
    }
}

Here is an output for the currency format using the Locale.CANADA and Locale.GERMANY.

Currency in Canada : $1,500.00
Currency in Germany: 1.500,00 €

How do I create a Locale object using a variant?

By Wayan in Core API, Util Package 0 Comment

Font differences may force you to use different characters on different platforms. You could then define the Locale objects with the variant codes to identify those differences. The variant codes conform to no standard. They are arbitrary and specific to your application. If you create Locale objects with variant codes only your application will know how to deal with them.

In this example instead of demonstrating to use a different font for different platform we simplify it to just print a different message. We create three different resource bundles for each platform, the Birthday_fr_FR_UNIX.properties, Birthday_fr_FR_MAC.properties and Birthday_fr_FR_WIN.properties. These files will contains different message for each platform.

package org.kodejava.util;

import java.util.Locale;
import java.util.ResourceBundle;

public class LocalePlatform {
    public static void main(String[] args) {
        ResourceBundle res;
        String language = "fr";
        String country = "FR";

        // Construct a locale from language, country, variant. Where the variant
        // can be a variant vendor and browser specific code.
        Locale unix = new Locale(language, country, "UNIX");
        res = ResourceBundle.getBundle("Birthday", unix);
        System.out.println("UNIX: " + res.getString("birthday"));

        Locale mac = new Locale(language, country, "MAC");
        res = ResourceBundle.getBundle("Birthday", mac);
        System.out.println("MAC : " + res.getString("birthday"));

        Locale windows = new Locale(language, country, "WIN");
        res = ResourceBundle.getBundle("Birthday", windows);
        System.out.println("WIN : " + res.getString("birthday"));
    }
}

Here are the contents of the resource bundle files:

Birthday_fr_FR_UNIX.properties

birthday=Unix, Joyeux anniversaire à vous!

Birthday_fr_FR_MAC.properties

birthday=Mac, Joyeux anniversaire à vous!

Birthday_fr_FR_WIN.properties

birthday=Windows, Joyeux anniversaire à vous!

How do I get all available Locale language codes?

By Wayan in Core API, Util Package 0 Comment

When you want to internationalize your application, you need to know the language code and country code. These codes will be used as the properties file name (the file name must be ended in language_COUNTRY.properties). Here is an example that show how to get all supported language’s code.

package org.kodejava.util;

import java.util.Locale;

public class LocaleCountryLanguageCode {
    public static void main(String[] args) {
        // Gets an array of all installed locales. The returned array represents
        // the union of locales supported by the Java runtime environment and by 
        // installed LocaleServiceProvider implementations.
        Locale[] locales = Locale.getAvailableLocales();

        for (Locale locale : locales) {
            System.out.printf("Locale name: %s = %s_%s%n",
                    locale.getDisplayName(), locale.getLanguage(), locale.getCountry());
        }
    }
}

Here are some of the results produces by the code above:

...
Locale name: Kikuyu (Latin, Kenya) = ki_KE
Locale name: Spanish (Brazil) = es_BR
Locale name: Koyra Chiini (Mali) = khq_ML
Locale name: English (Solomon Islands) = en_SB
Locale name: Tibetan (Tibetan, China) = bo_CN
Locale name: Cherokee (United States) = chr_US
Locale name: Kinyarwanda (Rwanda) = rw_RW
Locale name: Tachelhit (Tifinagh, Morocco) = shi_MA
Locale name: Arabic (Iraq) = ar_IQ
Locale name: Nyankole = nyn_
...

How do I use the SortedMap interface?

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

import java.util.*;

public class SortedMapDemo {
    public static void main(String[] args) {
        SortedMap<String, String> sorted = new TreeMap<>();
        sorted.put("United States", "New York");
        sorted.put("United Kingdom", "London");
        sorted.put("Netherlands", "Amsterdam");
        sorted.put("Japan", "Tokyo");
        sorted.put("France", "Paris");

        // Gets the first(lowest) key currently in this map
        String firstKey = sorted.firstKey();

        // Gets the last (highest) key currently in this map
        String lastKey = sorted.lastKey();

        System.out.println("First key: " + firstKey);
        System.out.println("Last key : " + lastKey);

        // Gets a view of the portion of this map whose keys range
        // from fromKey(Japan), inclusive, to toKey(United Kingdom),
        // exclusive. (If fromKey and toKey are equal, the returned
        // map is empty.)
        SortedMap<String, String> sub = sorted.subMap("Japan",
                "United Kingdom");
        Set<String> subKeys = sub.keySet();
        System.out.println("\nSub Map: ");
        System.out.println("============");
        for (String key : subKeys) {
            System.out.println(key);
        }

        // Gets a view of the portion of this map whose keys are
        // strictly less than toKey(in this example is Netherlands)
        SortedMap<String, String> head = sorted.headMap("Netherlands");
        Set<String> headKeys = head.keySet();
        System.out.println("\nHead Map:");
        System.out.println("============");
        for (String key : headKeys) {
            System.out.println(key);
        }

        // Gets a view of the portion of this map whose keys are
        // strictly greater than or equal fromKey(in this example
        // is Netherlands)
        SortedMap<String, String> tail = sorted.tailMap("Netherlands");
        Set<String> tailKeys = tail.keySet();
        System.out.println("\nTail Map:");
        System.out.println("============");
        for (String key : tailKeys) {
            System.out.println(key);
        }
    }
}

Here is the output of the program:

First key: France
Last key : United States

Sub Map: 
============
Japan
Netherlands

Head Map:
============
France
Japan

Tail Map:
============
Netherlands
United Kingdom
United States

How do I convert a java.util.Vector into an array?

By Wayan in Core API, Util Package 0 Comment

This example demonstrates how to convert a Vector object into an array. You can use the Vector.copyInto(Object[] array) method to create a copy of the Vector object in array form.

package org.kodejava.util;

import java.util.Vector;

public class VectorToArray {
    public static void main(String[] args) {
        Vector<Integer> vector = new Vector<>();
        vector.add(10);
        vector.add(20);
        vector.add(30);
        vector.add(40);
        vector.add(50);

        // Declares and initializes an Integer array.
        Integer[] numbers = new Integer[vector.size()];

        // Copies the components of this vector into the specified
        // array of Integer
        vector.copyInto(numbers);

        for (Integer number : numbers) {
            System.out.println("Number: " + number);
        }
    }
}

The result of the code snippet above:

Number: 10
Number: 20
Number: 30
Number: 40
Number: 50

How do I use the shift right “>>” operator?

By Wayan in Basic, Core API 0 Comment

The signed shift right operator >> shifts a bit pattern to the right. This operator operates with two operand, the left-hand operand to be shifted and the right-hand operand tells how much position to shift.

Shifting a 1000 bit pattern using the >> operator 2 position will produce a 0010 bit pattern. The signed shift right operator produce a result that equals to dividing a number by 2.

package org.kodejava.basic;

public class SignedRightShiftOperator {
    public static void main(String[] args) {
        // The binary representation of 32 is
        // "00000000000000000000000000100000"
        int number = 32;
        System.out.println("number       = " + number);
        System.out.println("binary       = " +
                Integer.toBinaryString(number));

        // Using the shift right operator we shift the bits
        // four times to the right which resulting the result
        // of "00000000000000000000000000000010"
        int shiftedRight = number >> 4;
        System.out.println("shiftedRight = " + shiftedRight);
        System.out.println("binary       = " +
                Integer.toBinaryString(shiftedRight));
    }
}

The result of the code snippet:

number       = 32
binary       = 100000
shiftedRight = 2
binary       = 10

How do I use the shift left “<<" operator?

By Wayan in Basic, Core API 2 Comments

The signed shift left operator << shifts a bit pattern to the left. This operator operates with two operand, the left-hand operand to be shifted and the right-hand operand tells how much position to shift.

Shifting a 0010 bit pattern using the << operator 2 position will produce a 1000 bit pattern. The signed shift left operator produce a result that equals to multiplying a number by 2, which double the value of a number.

package org.kodejava.basic;

public class SignedLeftShiftOperator {
    public static void main(String[] args) {
        // The binary representation of 2 is "0010"
        int number = 2;
        System.out.println("number      = " + number);
        System.out.println("binary      = " +
                Integer.toBinaryString(number));

        // Using the shift left operator we shift the bits two
        // times to the left. This will shift the "0010" into
        // "1000"
        int shiftedLeft = number << 2;
        System.out.println("shiftedLeft = " + shiftedLeft);
        System.out.println("binary      = " +
                Integer.toBinaryString(shiftedLeft));
    }
}

The result of the code snippet:

number      = 2
binary      = 10
shiftedLeft = 8
binary      = 1000

How do I use the unary bitwise complement “~” operator?

By Wayan in Basic, Core API 0 Comment

The unary bitwise complement operator (~) inverts a bit pattern; it can be applied to any of the integral types, making every 0 a 1 and every 1 a 0.

For example, an integer contains 32 bits; applying this operator to a value whose bit pattern is 00000000000000000000000000001000 would change its pattern to 11111111111111111111111111110111.

package org.kodejava.basic;

public class UnaryBitwiseComplementOperator {
    public static void main(String[] args) {
        // An integer type contains 32 bit information.
        // 8 = 00000000000000000000000000001000
        int number = 8;
        System.out.println("number = " + number);
        System.out.println(Integer.toBinaryString(number));

        // Using the ~ operator inverts the number by change the
        // every "0" to "1" and every "1" to "0".
        // 00000000000000000000000000001000
        // 11111111111111111111111111110111
        //
        int invertedNumber = ~number;
        System.out.println("invertedNumber = " + invertedNumber);
        System.out.println(Integer.toBinaryString(invertedNumber));
    }
}

The result of the code snippet:

number = 8
1000
invertedNumber = -9
11111111111111111111111111110111