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.

• 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.