I spent some time working on this same problem yesterday. The best and most reliable solution I was able to come up with was to install google-java-format into my path and then use the RunOnSave extension to invoke the binary for files with the .java extension.

Install emeraldwalk/vscode-runonsave:

$ code --install-extension emeraldwalk.RunOnSave

Install google-java-format for your system:

# Example using Homebrew on OS X
$ brew install google-java-format

Configure RunOnSave in Visual Studio Code settings:

{
  "emeraldwalk.runonsave": {
    "commands": [
      {
        "match": "\\.java$",
        "cmd": "google-java-format --replace ${file}"
      },
    ],
  },
}

I describe more of the methodology in this blog post.

This problem can be solve installing the google-java-format Plugin.

1. Open plugins window (CTRL+Shift+A): plugins

2. Click on browse repositories.

3. Search for google-java-format

4. Install the plugin.

5. Restart the IDE.

6. Enable the plugin executing the action (Ctrl+Shift+A): Reformat with google-java-format Update: in the newer version of the plugin select Reformat since the plugin overrides / enhances the functionality of the standard "Reformat" command.

Additional notes from the google-java-format README

The plugin will be disabled by default. To enable it in the current project, go to File→Settings...→google-java-format Settings (or IntelliJ IDEA→Preferences...→Other Settings→google-java-format Settings on macOS) and check the Enable google-java-format checkbox. (A notification will be presented when you first open a project offering to do this for you.)

To enable it by default in new projects, use File→Other Settings→Default Settings....