I apologize, but I must inform you that there is no JsonGetter 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 get JSON data 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.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonGetterExample {
    public static void main(String[] args) throws IOException {
        String json = "{\"firstName\":\"John\",\"lastName\":\"Doe\",\"age\":30}";

        // Create an ObjectMapper instance
        ObjectMapper mapper = new ObjectMapper();

        // Parse the JSON string to a JsonNode object
        JsonNode jsonNode = mapper.readTree(json);

        // Get the value of the "firstName" field
        String firstName = jsonNode.get("firstName").asText();

        // Print the value
        System.out.println("First name: " + firstName);
    }
}

This example uses the ObjectMapper class from the Jackson library to parse a JSON string to a JsonNode object. It then uses the get() method of the JsonNode class to get the value of the "firstName" field and the asText() method to get the value of the node as a string.

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