Statement lambda can be replaced with expression lambda

Question

I do user and invitation validation using the Optional facility

@DeleteMapping("/friends/{username}") public HttpEntity<Boolean> removeFriend(         @ApiParam(value = "The user's name", required = true) @PathVariable String username ) {     Long fromId = authorizationService.getUserId();      return userService.findByUsername(username)             .map(user -> {                  return friendshipService.findFriendship(fromId, user.getId())                         .map(friendship -> {                             friendshipService.removeFriendship(friendship);                              friendship.setToId(friendship.getFromId());                             friendship.setFromId(friendship.getToId());                              friendshipService.removeFriendship(friendship);                              return ResponseEntity.ok(true);                         }).orElseGet(() -> ResponseEntity.notFound().build());             }).orElseThrow(() -> new ResourceNotFoundException("User not found")); 

However, IntelliJ is colouring my grey return, But when I remove the return, it highlights to me that there is no return.

Could someone explain how it works and what is it all about?

Answer 1

Your statement lambda

param -> { return expression; } 

can be changed to an expression lambda:

param -> expression 

Simple, isn't it? Note, that the curly brackets and the semicolon need to be removed.