How to access aem java logs in dev environment. Do we need system/console access for it?

Hi, 

If you are working with AEMaaCS you can download the logs from the the developer console which is part of cloud mananger, here you can find a detailed explanation of how to do it: https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/implementing/using-cloud-manager/manage-logs.html?lang=en. 

Also, you can do it using the command line interface:
 https://experienceleague.adobe.com/docs/experience-manager-learn/cloud-service/debugging/debugging-aem-as-a-cloud-service/logs.html?lang=en#aio-cli-download-logs 

On the other hand, if you are using an onPremise version of AEM, you most likely will have to get access to the server where AEM is running to get the logs files, you could also use the access to /system/console in this scenario, but this would let you see the current log, not former ones.

HOpe this helps