IntelliJ not recognizing a particular file correctly, instead its stuck as a text file

Please ensure that this file (or a pattern that represents it) is not listed under

Settings → Editor → File Types→ Text files

For OS X

Preferences → Editor → File Types→ Text files

Step 1: Click "File"==> "Settings"

Step 2: Expand "Editor" & Click "File Types"

Step 3: You will see all file types on Right. Navigate to the "Text" entry and lick it

Step 4: You should able to see your file name on the bottom of Registered Patterns (lower box)

Step 5: Remove your file from the Registered Patterns. The problem should be solved and let you rename with fileName.java

Step 6: If not, delete the file from the project and create it again with name fileName

Source

OSX:

Preferences > Editor > File Types > Text

Windows:

Settings > Editor > File Types > Text Files