[BUG] [Java] Object defaults with enum properties generate invalid fluent builder expressions

[nh-ive]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When a schema defines a default value for an object that contains an enum property, the Java generator generates an invalid fluent builder expression.

Expected output:

private OutputFormat format = new OutputFormat().order(OutputFormat.OrderEnum.SIMILARITY).limit(10);

Actual output:

private OutputFormat format = new OutputFormat().order("SIMILARITY").limit(10);

openapi-generator version

7.24.0-SNAPSHOT (latest master)

OpenAPI declaration file content or url

openapi: "3.1.0"
info:
  title: Enum Default Issue Demo
  version: 1.0.0

components:
  schemas:
    OutputFormat:
      type: object
      properties:
        order:
          type: string
          enum:
            - IMPORTANCE
            - SIMILARITY
        limit:
          type: integer
      default:
        order: SIMILARITY
        limit: 10

    Formatter:
      type: object
      properties:
        format:
          $ref: '#/components/schemas/OutputFormat'

Generation Details

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>7.24.0-SNAPSHOT</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/api/OpenApi.yaml</inputSpec>
                <generatorName>java</generatorName>
                <library>native</library>
                <skipValidateSpec>true</skipValidateSpec>
                <generateApiTests>false</generateApiTests>
                <generateModelTests>false</generateModelTests>
                <configOptions>
                    <useJakartaEe>true</useJakartaEe>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

Steps to reproduce

Related issues/PRs

Suggest a fix

The issue seems to be that the if statement in the method toObjectDefaultValue of the class AbstractJavaCodegen is missing a case for enums.