To download the Java client for v2 API using OpenAPI Generator, follow these steps:

1. Install OpenAPI Generator CLI using npm:

npm install @openapitools/openapi-generator-cli

2. Create a new directory for your project and navigate to it in your terminal/command prompt.

3. Generate the Java client library using OpenAPI Generator CLI:

openapi-generator generate -i path/to/your/openapi-specification.yaml -g java -o output

Replace path/to/your/openapi-specification.yaml with the actual path to your OpenAPI specification file, and output with the desired directory for the generated Java client library.

4. Once the generation is complete, you can find the generated Java client jar file in the output directory.

Note: Make sure to replace path/to/your/openapi-specification.yaml with the actual path to your OpenAPI specification file.