In Java, the DecimalFormat class is used for formatting and parsing decimal numbers in a locale-sensitive way. The DecimalFormat class is part of the java.text package, and provides a way to format and parse decimal numbers based on the rules of a specific locale.

The DecimalFormat class provides several pre-defined formats for common decimal number representations, such as currency and percent formats. Here's an example that demonstrates how to use the DecimalFormat class to format a decimal number in the currency format for a specific locale:

import java.util.*;
import java.text.*;

public class DecimalFormatDemo {
    public static void main(String[] args) {
        double amount = 1234.56;
        DecimalFormat df = (DecimalFormat) NumberFormat.getCurrencyInstance(new Locale("en", "US"));
        String formattedAmount = df.format(amount);
        System.out.println(formattedAmount);
    }
}

In this example, a double value representing an amount of money is formatted using the currency format for the US locale. The output of this code is:

$1,234.56

As you can see, the amount is formatted with the dollar sign and thousands separators that are common in the US.

The DecimalFormat class also provides methods for parsing decimal number strings back into double values. Here's an example that demonstrates how to use the DecimalFormat class to parse a decimal number string into a double value:

import java.util.*;
import java.text.*;

public class DecimalFormatDemo {
    public static void main(String[] args) {
        String amountString = "$1,234.56";
        DecimalFormat df = (DecimalFormat) NumberFormat.getCurrencyInstance(new Locale("en", "US"));
        try {
            double amount = df.parse(amountString).doubleValue();
            System.out.println(amount);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

In this example, a currency string is parsed into a double value using the currency format for the US locale. The output of this code is:

1234.56

The DecimalFormat class provides several other methods and options for formatting and parsing decimal numbers, such as specifying the minimum and maximum number of integer and fraction digits, controlling the rounding mode, and specifying the pattern of the format.

In summary, the DecimalFormat class in Java provides a way to format and parse decimal numbers in a locale-sensitive way. By using the DecimalFormat class, developers can create software applications that correctly handle decimal numbers in different languages and regions, and that provide a consistent and appropriate user experience for users from different cultures.