Here is an example of using the JsonTypeResolver class from the com.fasterxml.jackson.databind package in the Jackson library for Java:

import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.fasterxml.jackson.databind.jsontype.JsonTypeResolver;

public class Example {
    public static void main(String[] args) throws JsonMappingException {
        ObjectMapper mapper = new ObjectMapper();
        TypeFactory typeFactory = mapper.getTypeFactory();
        JsonTypeResolver typeResolver = mapper.getDeserializationConfig().getTypeResolver();
        
        // example input JSON string
        String jsonInput = "{\"name\":\"John\",\"age\":30}";

        // use the type resolver to determine the type of the JSON input
        JsonNode root = mapper.readTree(jsonInput);
        JavaType type = typeResolver.resolveType(root, typeFactory);
        System.out.println("Type of JSON input: " + type.toString());
    }
}

This example uses an ObjectMapper to read JSON input and determine its type. The JsonTypeResolver is used to resolve the type of the input JSON.