Convert a Java Object to a List of an Object

Question

I am trying to convert a java object into a a List of Object. My current object is the ff.

@Data
@AllArgsConstructor
@NoArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonNaming(PropertyNamingStrategy.UpperCamelCaseStrategy.class)
public final class GetCreditCardInfo {

    @JsonAlias("ns:return")
    private List<CreditCardDetails> details;

    @JsonAlias("ns:return")
    private CreditCardDetails detailsObject;

}

What the code does above is get the object or list of objects in the response. I plan on just converting an object into a List of objects if the details variable doesnt have a value at all.

I'm doing this since our southbound APIs throw either an Object or a List of Objects seen below.

For the existing implementation that I have, I just want to just convert the object into a List so that if the API threw an Object response. My existing implementation for a List of Object would still work since the api that threw an object will still be read as a single List of object in my API. Is there a way to convert my Object to List of Objects?

Answer 1

tl;dr

List.of( myCreditCardDetails )

List.of

Java 9 and later provides several handy List.of methods on the List interface for instantiating an unmodifiable list.

To make an unmodifiable list containing a single object:

List< CreditCardDetails > list = List.of( myCreditCardDetails ) ;

To make an empty unmodifiable list:

List< CreditCardDetails > list = List.of() ;

To make an unmodifiable list containing multiple objects:

List< CreditCardDetails > list = List.of( aliceCreditCardDetails , bobCreditCardDetails , carolCreditCardDetails , davisCreditCardDetails ) ;

You can pass up to around 64,000 elements according to What is the maximum of number of arguments for varargs in java?.

To make an unmodifiable list from an array:

List< CreditCardDetails > list = List.of( arrayOfCreditCardDetailsObjects ) ;

To make an unmodifiable list copied from a modifiable list, call List.copyOf.

List< CreditCardDetails > list = List.copyOf( otherModifiableList ) ;