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

The NumberFormat class is an abstract class, so you cannot create an instance of it directly. Instead, you can use the factory methods provided by the NumberFormat class to create instances of its subclasses, such as DecimalFormat and ChoiceFormat.

Here's an example that demonstrates how to use the NumberFormat class to format a number in the percent format for a specific locale:

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

public class NumberFormatDemo {
    public static void main(String[] args) {
        double percentage = 0.75;
        NumberFormat nf = NumberFormat.getPercentInstance(new Locale("en", "US"));
        String formattedPercentage = nf.format(percentage);
        System.out.println(formattedPercentage);
    }
}

In this example, a double value representing a percentage is formatted using the percent format for the US locale. The output of this code is:

75%

As you can see, the percentage is formatted with the percent sign and no decimal places, which are common in the US.

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

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

public class NumberFormatDemo {
    public static void main(String[] args) {
        String percentageString = "75%";
        NumberFormat nf = NumberFormat.getPercentInstance(new Locale("en", "US"));
        try {
            double percentage = nf.parse(percentageString).doubleValue();
            System.out.println(percentage);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

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

0.75

The NumberFormat class provides several other methods and options for formatting and parsing numbers, such as specifying the minimum and maximum number of integer and fraction digits, controlling the rounding mode, and handling negative numbers and zero values.

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