nullcheck.java

package cz.vmencik.sandbox.nullcheck;

interface AuthorizedUser {
  User getUser();
}

interface User {
	Group getGroup();
}

interface Group {
	String getName();
}

public class NullcheckJava {
	
	public String getGroupName1(AuthorizedUser authUser) {
		if (authUser == null) {
			return null;
		}
		User user = authUser.getUser();
		if (user == null) {
			return null;
		}
		Group group = user.getGroup();
		if (group == null) {
			return null;
		}
		return group.getName();
	}
	
	public String getGroupName2(AuthorizedUser authUser) {
		if (authUser != null) {
			User user = authUser.getUser();
			if (user != null) {
				Group group = user.getGroup();
				if (group != null) {
					return group.getName();
				}
			}
		}
		return null;
	}
}

nullcheck.scala

package cz.vmencik.sandbox

trait AuthorizedUser {
  def user: Option[User]
}

trait User {
  def group: Option[Group]
}

trait Group {
  def name: String
}

object OptionExample {
  
  def getGroupName1(maybeAuthUser: Option[AuthorizedUser]): Option[String] = {
    maybeAuthUser.flatMap(_.user.flatMap(_.group.map(_.name)))
  }

  def getGroupName2(maybeAuthUser: Option[AuthorizedUser]): Option[String] = {
    maybeAuthUser.flatMap { authUser =>
      authUser.user.flatMap { user =>
        user.group.map { group =>
          group.name
        }
      }
    }
  }

  def getGroupName3(maybeAuthUser: Option[AuthorizedUser]): Option[String] = {
    for {
      authUser <- maybeAuthUser
      user <- authUser.user
      group <- user.group
    } yield group.name
  }
  
}