[JAVA] Problem generating model where default value is specified for date property

Description

Model properties that are dates generate invalid Java code where a default value is specified.

Swagger-codegen version

v3.0.20
(unknown whether this is a regression)

Swagger declaration file content or url

{
    "openapi": "3.0.1",
    "paths": {},
    "components": {
        "schemas": {
            "Request": {
                "type": "object",
                "properties": {
                    "endDate": {
                        "type": "string",
                        "format": "date",
                        "default": "1900-01-01"
                    },
                    "startDate": {
                        "type": "string",
                        "format": "date"
                    }
                }
            }
        }
    }
}

Command line used for generation

java -jar swagger-codegen-cli-3.0.20.jar generate -i test.json -l java -o .\output --additional-properties dateLibrary=java8-localdatetime

Steps to reproduce

Run the command above;
View generated Request.java which contains the following invalid variable initialization:

@javax.annotation.Generated(value = "io.swagger.codegen.v3.generators.java.JavaClientCodegen", date = "2020-07-14T16:43:41.079+10:00[Australia/Sydney]")
public class Request {
  @SerializedName("endDate")
  private LocalDate endDate = Mon Jan 01 00:00:00 AEST 1900;
 
  @SerializedName("startDate")
  private LocalDate startDate = null;
  ...

Related issues/PRs

None known.

Suggest a fix/enhancement

Removing the default from the Swagger file stops the problem, but the file comes from a third party, and editing it is not desirable.

Start with the provided test.json and run the Swagger Codegen CLI command using dateLibrary=java8-localdatetime. Inspect the generated Request.java, especially the endDate initialization; done means the date default produces valid Java while retaining the declared default value.