I apologize, but there is no such class as "NumberOutput" in the Apache Commons IO library. It seems that you might be confusing it with other class or package. Apache Commons IO focuses on providing utility classes for file and I/O operations, and it doesn't have a class specifically for outputting numbers.

Java provides several classes for outputting numbers such as Integer.toString(), Long.toString(), Double.toString(), etc. You can use these methods to convert a number to a string.

Here is an example of using the Integer.toString() method to convert an integer to a string:

public class NumberOutputExample {
    public static void main(String[] args) {
        int number = 123;
        String output = Integer.toString(number);
        System.out.println(output);
    }
}

This will output:

123

You can also use the Long.toString(), Double.toString(), Float.toString() and other toString methods to convert long, double and float values respectively.

You can also use the NumberFormat class to format numbers in a locale-specific format.