Once, you delete a file, it goes to the Trash folder. At any time, if you need a deleted file, you can restore the file by dragging the file out of Trash. However, sometimes, while deleting, if the size of the file is very big to be contained inside Trash folder or you have hit the set commands, like 'Command+Shift+Option+Delete', then the file gets completely deleted without going into the Trash. Apart from this, at times, you just clean your Trash completely by choosing the 'Empty Trash' option from the Finder menu.

In such cases, after emptying the Trash, Mac does not have any option to restore the deleted files. 
However, you can use this powerful Mac Data Recovery (I've downloaded and used it, 100% safe) tool to recover all your deleted files even after emptying the Trash folder.

Steps to Recover data after emptying the trash:

Step 1: Download this Mac Data Recovery Software and install into on your mac.

Step 2: Run this Macintosh Data Recovery software and from the main interface, click the 'Deleted File Recovery' icon.

Step3: Another interface opens. Choose the volume, from which you need to recover the deleted file and click on the 'Continue' button to initiate the scanning operation.

Step 4: The software scans the selected volume and shows all the recoverable deleted files/folders in a tree view. (Only Preview of recoverable deleted files is available in the demo version of the software)
To recover the deleted files you need to activate the software. After activating the software

Step 5: Select the files, you want to recover and click the 'Recover' button.

Step 6: Provide the location, when the software asks you to specify the location, where the recovered files will be saved. By default, all the recovered files get saved in a folder named 'Root' at the specified location.

Done.