This example will explain how to null out a non-required field by sending a null value in your request using the Java toolkit.
1. Make sure you have the gson.JsonNull class imported into your .java class file.
import com.google.gson.JsonNull;
2. Create a new JSON Object.
JsonObject newDefectUpdate = new JsonObject();
3. Set the property using the add method and the JsonNull.INSTANCE class constant.
newDefectUpdate.add("c_CustomDate", JsonNull.INSTANCE );
4. Send your request for the artifact.
UpdateRequest updateRequest = new UpdateRequest("/defect/<OID>", newDefectUpdate);