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copied!<p>Let's start with the <strong>"Singleton pattern"</strong>:</p> <pre><code>object SomeSingleton //That's it </code></pre> <hr> <p>I would additionally propose the <strong>"Using-functions-of-higher-order pattern"</strong>. Instead of e. g. iterating through a collection by yourself you supply functions to the methods the classes provide.</p> <p>In Scala you basically say what you intend to do: </p> <pre><code>//declare some example class case class Person(name: String, age: Int) //create some example persons val persons = List(Person("Joe", 42), Person("Jane", 30), Person("Alice", 14), Person("Bob", 12)) //"Are there any persons in this List, which are older than 18?" persons.exists(_.age > 18) // => Boolean = true //"Is every person's name longer than 4 characters?" persons.forall(_.name.length > 4) // => Boolean = false //"I need a List of only the adult persons!" persons.filter(_.age >= 18) // => List[Person] = List(Person(Joe,42), Person(Jane,30)) //"Actually I need both, a list with the adults and a list of the minors!" persons.partition(_.age >= 18) // => (List[Person], List[Person]) = (List(Person(Joe,42), Person(Jane,30)),List(Person(Alice,14), Person(Bob,12))) //"A List with the names, please!" persons.map(_.name) // => List[String] = List(Joe, Jane, Alice, Bob) //"I would like to know how old all persons are all together!" persons.foldLeft(0)(_ + _.age) // => Int = 98 </code></pre> <p>Doing this in Java would have meant touching the elements of a collection yourself and mix your application logic with flow control code.</p> <p><a href="http://www.scala-lang.org/docu/files/collections-api/collections.html" rel="noreferrer">More information</a> about the Collection classes.</p> <hr> <p>This nice <a href="http://lamp.epfl.ch/~imaier/pub/DeprecatingObserversTR2010.pdf" rel="noreferrer">EPFL paper</a> about <strong>Deprecating the Observer Pattern</strong> might be of interest, too.</p> <hr> <p><strong><a href="http://lambda-the-ultimate.org/node/4039" rel="noreferrer">Typeclasses</a></strong> are one approach to structure common features of classes where inheritance doesn't really fit.</p>

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