I apologize, but I must inform you that there is no JsonFormat class in the Apache Commons IO library. This library provides a set of I/O utilities such as file manipulation, file filters, and file comparators, but it does not have any specific functionality for working with JSON.

If you are looking for a way to format JSON in Java, you can use a third-party library such as Jackson or Gson. Here is an example using the Jackson library:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class JsonFormatExample {
    public static void main(String[] args) throws JsonProcessingException {
        // Create an object to be serialized
        Person person = new Person("John", "Doe", 30);

        // Create an ObjectMapper instance
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT); // Enable pretty-printing
        
        // Serialize the object to a JSON string
        String json = mapper.writeValueAsString(person);

        // Print the JSON string
        System.out.println(json);
    }
}

class Person {
    private String firstName;
    private String lastName;
    private int age;

    public Person(String firstName, String lastName, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }

    // Getters and setters
    // ...
}

This example uses the ObjectMapper class from the Jackson library to convert a Person object to a JSON string, it uses the SerializationFeature.INDENT_OUTPUT to format the json string in a pretty format.

Note that there are other libraries like Gson and JSON-simple that have similar functionality.