Using format flags to format negative number in parentheses

In this example we are going to learn to use a java.util.Formatter to format negative number in parentheses. The Formatter can use a format flags to format a value. To display a negative number in parentheses we can user the ( flag. This flag display negative number inside parentheses instead of using the - symbol.

The following code snippet below will show you how to do it. We start the example by using the Formatter object and simplified using the format() method of the String class.

package org.kodejava.example.util;

import java.util.Formatter;
import java.util.Locale;

public class FormatNegativeNumber {
    public static void main(String[] args) {
        // Creates an instance of Formatter, format the number using the
        // format and print out the result.
        Formatter formatter = new Formatter();
        formatter.format("%(,.2f", -199.99f);
        System.out.println("number1 = " + formatter);

        // Use String.format() method instead of creating an instance of
        // Formatter. Format a negative number using Germany locale.
        String number2 = String.format(Locale.GERMANY, "%(,8.2f", -49.99);
        System.out.println("number2 = " + number2);

        // Format number using Indonesian locale. The thousand separator is "."
        // in Indonesian number.
        String number3 = String.format(new Locale("id", "ID"), "%(,d", -10000);
        System.out.println("number3 = " + number3);
    }
}

The result of this code snippet:

number1 = (199.99)
number2 =  (49,99)
number3 = (10.000)

How do I parse negative number in parentheses?

In financial application negative numbers are often represented in parentheses. In this post we will learn how we can parse or convert the negative number in parentheses to produce the represented number value. To parse text / string to a number we can use the java.text.DecimalFormat class.

Beside number in parentheses, in this example we also parse negative number that use the minus sign with the currency symbol like $. Let’s jump to the code snippet below:

package org.kodejava.example.text;

import java.text.DecimalFormat;

public class NegativeNumberParse {
    // Pattern for parsing negative number.
    public static final String PATTERN1 = "#,##0.00;(#,##0.00)";
    public static final String PATTERN2 = "$#,##0.00;-$#,##0.00";

    public static void main(String[] args) throws Exception {
        DecimalFormat df = new DecimalFormat(PATTERN1);

        String number1 = "(1000)";
        String number2 = "(1,500.99)";

        System.out.println("number1 = " + df.parse(number1));
        System.out.println("number2 = " + df.parse(number2));

        df = (DecimalFormat) DecimalFormat.getInstance();
        df.applyPattern(PATTERN2);

        String number3 = "-$1000";
        String number4 = "-$1,500.99";

        System.out.println("number3 = " + df.parse(number3));
        System.out.println("number4 = " + df.parse(number4));
    }
}

And here are the results of our code snippet above:

number1 = -1000
number2 = -1500.99
number3 = -1000
number4 = -1500.99

If you need to display or format negative numbers in parentheses you can take a look at the following example How do I display negative number in parentheses?.

How to use underscore in numeric literals?

Writing a long sequence of numbers in a code is a hard stuff to read. In the new feature introduced by JDK 7 we are now allowed to write numeric literals using the underscore character to break the numbers to make it easier to read.

You can see how to use underscore in numeric literals in the following examples. And you’ll see it for yourself that it really makes numbers easier to read.

package org.kodejava.example.basic;

public class UnderscoreNumericExample {
    public static void main(String[] args) {
        // Write numeric literals using underscore as an easier way
        // to read long numbers.
        int maxInt = 2_147_483_647;
        int minInt = -2_147_483_648;

        if (maxInt == Integer.MAX_VALUE) {
            System.out.println("maxInt = " + maxInt);
        }

        if (minInt == Integer.MIN_VALUE) {
            System.out.println("minInt = " + minInt);
        }

        // Write numbers in binary or hex literals using the
        // underscores.
        int maxIntBinary = 0B111_1111_1111_1111_1111_1111_1111_1111;
        int maxIntHex    =   0X7____F____F____F____F____F____F____F;

        System.out.println("maxIntBinary = " + maxIntBinary);
        System.out.println("maxIntHex    = " + maxIntHex);
    }
}

The results of the code snippet:

maxInt = 2147483647
minInt = -2147483648
maxIntBinary = 2147483647
maxIntHex    = 2147483647

How do I parse a number for a locale?

package org.kodejava.example.text;

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

public class LocaleNumberParse {
    public static void main(String[] args) {
        try {
            // In this example we are trying to parse a number string in a
            // defined format. Basically we want to covert the string for a
            // locale into a correct number value.
            Number number =
                NumberFormat.getNumberInstance(Locale.JAPAN).parse("25,000.75");

            // Just do some stuff with the number from the parse process
            if (number instanceof Long) {
                System.out.println("This number is instanceof Long and the " +
                    "value is: " + number.longValue());
            } else if (number instanceof Double) {
                System.out.println("This number is instanceof Double and the " +
                    "value is: " + number.doubleValue());
            }
        } catch (ParseException e) {
            e.printStackTrace();
        }

    }
}

How do I check if a string is a valid number?

When creating a program we will use a lot of string to represent our data. The data might not just information about our customer name, email or address, but will also contains numeric data represented as string. So how do we know if this string contains a valid number?

Java provides some wrappers to the primitive data types that can be used to do the checking.

package org.kodejava.example.lang;

public class NumericParsingExample {
    public static void main(String[] args) {
        String age = "15";
        String height = "160.5";
        String weight = "55.9";

        try {
            int theAge = Integer.parseInt(age);
            float theHeight = Float.parseFloat(height);
            double theWeight = Double.parseDouble(weight);

            System.out.println("Age   : " + theAge);
            System.out.println("Height: " + theHeight);
            System.out.println("Weight: " + theWeight);
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
    }
}

In the example code we use Integer.parseInt(), Float.parseFloat(), Double.parseDouble() methods to check the validity of our numeric data. If the string is not a valid number NumberFormatException will be thrown.

The result of our example:

Age   : 15
Height: 160.5
Weight: 55.9