public static List<ServiceInstance> getInstances(String serviceId) {
		return Optional.ofNullable(instancesMap.get(serviceId))
				.orElse(Collections.emptyList());
	}
Get instances for specific service.
@param serviceId service id
@return service instances
spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-nacos-discovery/src/main/java/com/alibaba/cloud/nacos/discovery/ServiceCache.java