Here is an example of using the SimpleSerializers class in the Jackson JSON library for Java:

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleSerializers;
import java.io.IOException;
import java.time.LocalDate;

public class LocalDateSerializer extends JsonSerializer<LocalDate> {

    @Override
    public void serialize(LocalDate value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        gen.writeString(value.toString());
    }
}

SimpleSerializers serializers = new SimpleSerializers();
serializers.addSerializer(LocalDate.class, new LocalDateSerializer());

In this example, we create a custom serializer for LocalDate objects, which converts them to strings in the format "yyyy-mm-dd". Then we create a new SimpleSerializers object and add our custom serializer to it using the addSerializer method. This allows us to use the custom serializer when serializing LocalDate objects with the Jackson library.