BoundedSetAndTest.scala

class BoundedSet2[T] {

  val data: util.LinkedList[T] = new util.LinkedList[T]()
  var capacity: Int = 0

  def BoundedSet(capacity: Int) {
    this.capacity = capacity;
  }

  def add(elem: T) {
    if (elem==null) throw new NullPointerException()

    data.remove(elem);

    if (data.size() == capacity) {
      data.removeFirst();
    }

    data.addLast(elem);
  }

  def contains(elem: T): Boolean = {
    data.contains(elem);
  }
}

object BoundedSetTestsScala {

  val set: BoundedSet[Int] = new BoundedSet[Int](3)

  def main(args: Array[String]): Unit = {
    testSingleElement
    testRepeatedElement
    testOverflowKeepsSecond
    testOverflowRemovesOldest
    testOverflowKeepsNewest
    testRenewal
  }

  def testSingleElement {
    set.add(1);
    assert(set.contains(1));
  }

  def testRepeatedElement {
    set.add(1);
    set.add(1);
    set.add(1);
    set.add(1);
    assert(set.contains(1));
  }

  def testOverflowKeepsSecond {
    set.add(1);
    set.add(2);
    set.add(3);
    set.add(4);
    assert(set.contains(2));
  }

  def testOverflowRemovesOldest {
    set.add(1);
    set.add(2);
    set.add(3);
    set.add(4);
    assert(!set.contains(1));
  }

  def testOverflowKeepsNewest {
    set.add(1);
    set.add(2);
    set.add(3);
    set.add(4);
    assert(set.contains(4));
  }

  def testRenewal {
    set.add(1);
    set.add(2);
    set.add(1);
    set.add(3);
    set.add(4);
    assert(set.contains(1));
  }
}