Вивчайте Getting Started with DecimalFormat | Controlling Numeric Output with DecimalFormat

When you need precise control over how numeric values appear in your Java applications, DecimalFormat is a powerful tool. Unlike String.format(), which provides general-purpose formatting for numbers and strings, DecimalFormat is specifically designed for flexible, locale-sensitive formatting of decimal numbers. You should choose DecimalFormat when you need to control decimal places, grouping separators (like commas in thousands), optional digits, or custom patterns that go beyond what String.format() offers. This makes it especially useful in financial applications, reports, or anywhere you want numbers to appear in a specific format for users.

Main.java


              12345678910111213
            
package com.example;

import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
        double number = 12345.6789;
        DecimalFormat formatter = new DecimalFormat("#,###.00");
        String formatted = formatter.format(number);
        System.out.println("Formatted number: " + formatted);
    }
}

The pattern string you provide to DecimalFormat determines exactly how numbers are displayed. Each character in the pattern has a specific meaning. For example, 0 means a digit is required, while # means a digit is optional and will not display extra zeros. The decimal point (.) sets where decimals appear, and commas (,) add grouping separators for thousands. By designing your pattern string, you can ensure your numbers are always formatted in a way that matches your application's needs.

Main.java


              12345678910111213141516
            
package com.example;

import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
        double value = 9876.5;

        DecimalFormat pattern1 = new DecimalFormat("0.00");
        DecimalFormat pattern2 = new DecimalFormat("#,###.##");

        System.out.println("Pattern '0.00': " + pattern1.format(value));
        System.out.println("Pattern '#,###.##': " + pattern2.format(value));
    }
}

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Suggested prompts:

Can you give some examples of common `DecimalFormat` patterns?

How do I use `DecimalFormat` in my Java code?

What are the main differences between `DecimalFormat` and `String.format()`?

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Main.java


              12345678910111213
            
package com.example;

import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
        double number = 12345.6789;
        DecimalFormat formatter = new DecimalFormat("#,###.00");
        String formatted = formatter.format(number);
        System.out.println("Formatted number: " + formatted);
    }
}

Main.java


              12345678910111213141516
            
package com.example;

import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
        double value = 9876.5;

        DecimalFormat pattern1 = new DecimalFormat("0.00");
        DecimalFormat pattern2 = new DecimalFormat("#,###.##");

        System.out.println("Pattern '0.00': " + pattern1.format(value));
        System.out.println("Pattern '#,###.##': " + pattern2.format(value));
    }
}

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Секція 2. Розділ 1

Getting Started with DecimalFormat

1. What is the main advantage of using DecimalFormat for numeric output?

2. Which pattern would you use to always show two decimal places?

3. How does DecimalFormat handle grouping separators (commas)?

Getting Started with DecimalFormat

1. What is the main advantage of using DecimalFormat for numeric output?

2. Which pattern would you use to always show two decimal places?

3. How does DecimalFormat handle grouping separators (commas)?