swagger codegen cli for openspec 3 - java language generation fails

Description

When I try to generate java stubs from a simple yml api definition I am getting the following error.

I am able to generate using other language types - but were hoping that the "java" language option will yield a set of stubs that are framework agnostic. I would like the generated stubs to be simply the model and an interface for the service.

Exception in thread "Thread-1" java.lang.RuntimeException: Could not generate model 'AppConfig'
at io.swagger.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:409)
at io.swagger.codegen.DefaultGenerator.generate(DefaultGenerator.java:728)
at io.swagger.codegen.cmd.Generate.run(Generate.java:331)
at java.lang.Thread.run(Unknown Source)
Caused by: java.util.regex.PatternSyntaxException: Illegal/unsupported escape sequence near index 3
v2\Java
^
at java.util.regex.Pattern.error(Unknown Source)
at java.util.regex.Pattern.escape(Unknown Source)
at java.util.regex.Pattern.atom(Unknown Source)
at java.util.regex.Pattern.sequence(Unknown Source)
at java.util.regex.Pattern.expr(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at java.util.regex.Pattern.(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at java.lang.String.replaceFirst(Unknown Source)
at io.swagger.codegen.DefaultGenerator.getHandlebars(DefaultGenerator.java:1014)
at io.swagger.codegen.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:744)
at io.swagger.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:396)
... 3 more

Swagger-codegen version

swagger-codegen-cli-3.0.0-20180515.103456-67.jar

Swagger declaration file content or url

openapi: 3.0.0
servers:
# Added by API Auto Mocking Plugin
  - description: SwaggerHub API Auto Mocking
    url: https://virtserver.swaggerhub.com/test/1.0.0  
info:
  description: Sample API
  version: "1.0.0"
  title: Sample API
  contact:
    email: test@email.com
  license:
    name: Apache 2.0
    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
tags:
  - name: admins
    description: Secured Admin-only calls
  - name: developers
    description: Operations available to regular developers
paths:
  /health:
    get:
      tags:
        - developers
      summary: Health endpoint
      operationId: health
      responses:
        '200':
          description: Health metrics for this endpoint
          content:
            application/json:
              schema:
                type: object                
                $ref: '#/components/schemas/HealthMetric'   
components:
  schemas:
    HealthMetric:
      type: object
      required:
        - reportGenerationEnabled
        - applicationVersion
        - configuration
        - hostname
      properties:
        reportGenerationEnabled:
          type: boolean
        applicationVersion:
          type: string
          example: "<artifact group>:<artifact name>:<artifact version>"
        hostname:
          type: string
        appConfig:
          $ref: '#/components/schemas/AppConfig'
    AppConfig:
      type: object
      required:
         - name
      properties:
        name:
          type: string
          description: A string       

Command line used for generation

java -jar swagger-codegen-cli-3.0.0-20180515.103456-67.jar generate -l java -i sample.yml -o ./dest

Steps to reproduce

Just run the command above.

Related issues/PRs

Suggest a fix/enhancement

Reproduce the failure with the provided sample.yml and the java -jar ... generate -l java command. Start at io.swagger.codegen.DefaultGenerator.getHandlebars and processTemplateToFile, using the stack trace in DefaultGenerator.java as the entry point. Done means Java generation completes without the PatternSyntaxException and produces the requested stubs.