As it mentioned in comments above, you cant remove fields of compiled class at runtime. Assuming you have to exclude some field from generated json, there I see two options:

1. Create a class with fields you want to be present in resulting json, copy required values from original object to a new created. This approach is called view model and allows you to decorate some object's data, hiding sensitive data from being exposed.
2. Depending on implementation of your serializer there may be annotations to exclude fields. @JsonIgnore may be placed on getter method, if you are using Jackson (default in spring boot). Second aproach requires significant less code, but the first one is more flexible.

You have two options:

1. Jackson works on setters-getters of fields. So, you can just remove getter of field which you want to omit in JSON. ( If you don't need getter at other place.)

2. Or, you can use the @JsonIgnore annotation of Jackson on getter method of that field and you see there in no such key-value pair in resulted JSON.

   @JsonIgnore
   public int getSecurityCode(){
      return securityCode;
   }
   

Not sure I understand your question completely, are you serializing an instance of this class, and do not want the Number_Address__c in the JSON?

If so, look at serialize(objectToSerialize, suppressApexObjectNulls)

You can do like below if you know the schema and heirarchy:

JsonObject jsonObj= gson.fromJson(json, JsonObject.class); jsonObj.getAsJsonObject("moreDetails").remove("secondName"); System.out.println(jsonObj.getAsString());

refer this for more info Remove key from a Json inside a JsonObject

else you need to write a dynamic function which will check each and every element of JSON object and try to find the secondName element in it and remove it.

So consider here as you have multiple nested objects then you need to write a function which will iterate over each element and check its type if its again a jsonObject call the same method recursively or iteratively to check against current element, in each check you need to also verify that the key, if it matches with the key which has to be removed then you can remove it and continue the same.

for a hint on how to check a value type of JSON see this How to check the type of a value from a JSONObject?

map won't work, since it's an intermediate operation, so it won't be executed unless it is followed by some terminal operation.

Use forEach:

Set<FilterEvent> filterEvents = preparation.getFilterEvents();
filterEvents.forEach(f->f.setFilterId(null));

However, if setFilterId expects an int, you can't pass null. You'll have to set it to some other value (0?).

Whichever method you use will always iterate through the list to remove your element. The only thing you can do is shorten and prettify your code as much as possible.

Here is a Java 8 one liner:

 boolean removed = myList.removeIf(pojo -> pojo.getAccountId().equals(provided));

@JsonInclude(JsonInclude.Include.NON_NULL)
public class TransactionHistoryBO { ... }

@JsonInclude(JsonInclude.Include.NON_NULL)
public class TransactionHistoryResponse { ... }

public class App {

    public static void main(String... args) throws JsonProcessingException {

        ObjectMapper om = new ObjectMapper();

        TransactionHistoryResponse thr = new TransactionHistoryResponse();
        TransactionHistoryBO thbo = new TransactionHistoryBO();
        thbo.setProductName("TEST");
        thr.setTransactions(new ArrayList<TransactionHistoryBO>());
        thr.getTransactions().add(thbo);
        System.out.print(om.writerWithDefaultPrettyPrinter().writeValueAsString(thr));
    }

}

Produces output :

{
  "transactions" : [ {
    "productName" : "TEST"
  } ]
}

No other annotation is used. Just add @JsonInclude annotation to classes not properties.

UPDATE:

Add a custom JacksonJsonProvider to your application

@Provider
public class CustomJsonProvider extends ResteasyJackson2Provider {

    @Override
    public void writeTo(Object value, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException {

        ObjectMapper mapper = locateMapper(type, mediaType);
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

        super.writeTo(value, type, genericType, annotations, mediaType, httpHeaders, entityStream);
    }

}

Register this provider in your web.xml

<context-param> 
    <param-name>resteasy.providers</param-name> 
    <param-value>com.package.CustomJsonProvider</param-value> 
</context-param>

Tested with and without this and it works.