use of a generic

generic interface

public interface Callback<T> {
    
    T loadData();
}

API layer interface uses generics

  public Object getObject(String key,Callback cacheCallback);

How the business layer specifically implements the interface

@RequestMapping(method = RequestMethod.GET, value = "/invoice-core/callback")
    @ResponseBody
    public Object callback(String key) throws BizException {
        Object res = redisCacheClient.getObject(key, new Callback<String>() {
            @Override
            public String loadData() {
                return "123";
            }
        });
        return res;
    }