During the coding process, it's convenient to have the code documentation close at hand. IntelliJ IDEA can extract the documentation straight from the source (using JavaDoc) or display the external documentation.
To view inline documentation, use Quick Documentation Lookup, which is available with Ctrl + Q (PC) or control + J (Mac). The dialog box will display the documentation for the symbol or method under the cursor, but only if the symbol or method has been provided with documentation comments. You can go through the quick documentation using the provided hyperlinks and arrow buttons to move back and forth through the pages. The Quick Documentation Lookup window can be pinned to become a tool window (we described this in the first chapter), as shown in the following screenshot:
Quick documentation lookup