Here is an example of how to use the StdDelegatingDeserializer class from the Jackson Databind library to deserialize an object using a custom deserializer:

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.deser.std.StdDelegatingDeserializer;

import java.io.IOException;

public class CustomDelegatingDeserializer extends StdDelegatingDeserializer {

    public CustomDelegatingDeserializer(JsonDeserializer<?> deser) {
        super(deser);
    }

    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        Object obj = super.deserialize(p, ctxt);
        // Do some custom processing on the object
        return obj;
    }

    @Override
    public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanDescription beanDesc) {
        return this;
    }
}

You can then use this custom deserializer by registering it with the ObjectMapper:

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
JsonDeserializer<MyClass> customDeserializer = new JsonDeserializer<MyClass>() {
    @Override
    public MyClass deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        // Custom deserialization logic
        return new MyClass();
    }
};
module.addDeserializer(MyClass.class, new CustomDelegatingDeserializer(customDeserializer));
mapper.registerModule(module);

Then you can deserialize your JSON to MyClass as follow:

MyClass myClass = mapper.readValue(jsonString, MyClass.class);

Please note that the above example is just a skeleton code, you may need to handle the exception and add proper validation based on your use case.

The StdDelegatingDeserializer allows you to delegate the deserialization of JSON to a different deserializer. In the example above, CustomDelegatingDeserializer is used to delegate the deserialization of MyClass objects to the customDeserializer which you can implement your own custom deserialization logic.

It is useful when you want to use a different deserializer for a specific class or when you want to add some custom logic to the deserialization process.