How to use the NumberFormat function for number formatting in Java

In Java, number formatting is a very common operation, such as displaying currency, percentage, scientific notation, etc. The NumberFormat class provided by Java can help us implement these number formatting operations. This article will explain how to use the NumberFormat function to perform number formatting operations.

Introduction to the NumberFormat class

The NumberFormat class is a number formatting class provided by the Java language and is located in the java.text package. The NumberFormat class provides many methods and properties to help us perform number formatting operations. Specifically, the NumberFormat class provides the following formatting types:

1. Currency formatting: Convert numbers to currency format, such as 1,000.00 yuan.
2. Percent formatting: Convert numbers to percentage format, such as 50.00%.
3. Scientific notation formatting: Convert the number to scientific notation format, such as 1.00000E 03.
4. Common number formatting: Format numbers according to a prescribed pattern, which may include delimiters, such as 1,000.

The NumberFormat class provides two ways to create objects: NumberFormat.getInstance() and NumberFormat.getNumberInstance(). Both methods can create a NumberFormat object, and we can implement number formatting operations by setting the properties and methods of the object.

Code example:

import java.text.NumberFormat;
public class NumberFormatExample {
    public static void main(String[] arg) {
        double amount = 1234567.89;
        NumberFormat nf = NumberFormat.getInstance();
        System.out.println("Number: " + amount);
        System.out.println("Formatted Number: " + nf.format(amount));
    }
}

Output result:

Number: 1234567.89
Formatted Number: 1,234,567.89

As shown in the above code, we can obtain a default number formatting object through the NumberFormat.getInstance() method, Then call the format() method to format the number.

Currency formatting

Currency formatting is the most commonly used formatting type in NumberFormat. Currency formatting can format numbers according to currency specifications, such as using currency symbols, thousandth separators, etc.

In NumberFormat, we can obtain a currency formatting object by calling the getCurrencyInstance() method. Code example:

import java.text.NumberFormat;
import java.util.Locale;
public class CurrencyFormatExample {
    public static void main(String[] arg) {
        double amount = 1234567.89;
        NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.CHINA);
        System.out.println("Number: " + amount);
        System.out.println("Formatted Currency: " + nf.format(amount));
    }
}

Output result:

Number: 1234567.89
Formatted Currency: ￥1,234,567.89

As shown in the above code, we obtain a currency formatting object by calling the getCurrencyInstance() method, and can set the formatting object used Locale(country).

Percent formatting

Percent formatting can format numbers according to percentage specifications, such as using percent signs, thousandth separators, etc.

In NumberFormat, we can obtain a percentage formatting object by calling the getPercentInstance() method. Code example:

import java.text.NumberFormat;
public class PercentFormatExample {
    public static void main(String[] arg) {
        double amount = 0.5;
        NumberFormat nf = NumberFormat.getPercentInstance();
        System.out.println("Number: " + amount);
        System.out.println("Formatted Percent: " + nf.format(amount));
    }
}

Output result:

Number: 0.5
Formatted Percent: 50%

As shown in the above code, we get a percentage formatting object by calling the getPercentInstance() method, and we can use the format() method to format the number Perform formatting operations.

Scientific notation formatting

Scientific notation formatting can format numbers according to scientific notation specifications, such as using exponent symbols, decimal points, etc.

In NumberFormat, we can obtain a scientific notation formatted object by calling the getScientificInstance() method. Code example:

import java.text.NumberFormat;
public class ScientificFormatExample {
    public static void main(String[] arg) {
        double amount = 1000;
        NumberFormat nf = NumberFormat.getScientificInstance();
        System.out.println("Number: " + amount);
        System.out.println("Formatted Scientific: " + nf.format(amount));
    }
}

Output result:

Number: 1000.0
Formatted Scientific: 1.000E3

As shown in the above code, we obtain a scientific notation formatted object by calling the getScientificInstance() method, and can use the format() method Perform formatting operations on numbers.

Ordinary number formatting

Ordinary number formatting can format numbers according to a pattern, which may include delimiters and so on.

In NumberFormat, we can obtain a common number formatting object by calling the getNumberInstance() method. Code example:

import java.text.NumberFormat;
public class NormalNumberFormatExample {
    public static void main(String [] arg) {
        double amount = 12345.6789;
        NumberFormat nf = NumberFormat.getNumberInstance();
        System.out.println("Number: " + amount);
        System.out.println("Formatted Number: " + nf.format(amount));
    }
}

Output result:

Number: 12345.6789
Formatted Number: 12,345.679

As shown in the above code, we obtain a common number formatting object by calling the getNumberInstance() method, and can use the format() method to Numbers are formatted.

Summary

This article introduces how to use the NumberFormat function to perform number formatting operations in Java. The NumberFormat class provides many methods and properties that can help us implement number formatting operations, including currency formatting, percentage formatting, scientific notation formatting, ordinary number formatting, and so on. In actual development, number formatting is a very common operation. We can use the NumberFormat class to easily and quickly implement number formatting.

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