IntelliJ-IdeaVim/doc/ideajoin-examples.md

Some examples of join command with ideajoin option enabled.
Put set ideajoin to your ~/.ideavimrc to enable this functionality.

Now, you can press J (shift+j) on a line or a selected block of text to join the lines together.

⚠️ This feature is language-specific. This means that the IDE should implement this feature for a particular language in order for the IDE to work as described below. If any of the examples provided below don't match your case, please file an issue in the project related to your IDE: https://youtrack.jetbrains.com/.
Here is a list of known requests: https://youtrack.jetbrains.com/issues?q=links:VIM-3214.

• Automatic join concatenated lines:

"Hello" +                 ->       "Hello world"
" world!"

• Nested if's:

if (a) {                  ->       if (a && b) {
  if (b) {                             ...
     ...                           }
  }
}

• Comments:

// Hello                  ->       // Hello world
// world

• Remove braces from one line for / if / while:

if (fail) {               ->       if (fail) return;
     return;
}

• Kotlin one line method:

fun myNumber(): Int {     ->       fun myNumber(): Int = 42
    return 42
}

• Join declaration and initialization:

int a;                    ->       int a = 5;
a = 5;

• Chain call:

sb.append("a");           ->       sb.append("a").append("b");
sb.append("b");

And other features provided by the plugins.