Java 9 Programming By Example

ColorManager

We jumped into the pool filled with collection classes from the implementation of the ColorManager class. Let's refresh the part of the class that is interesting for us now—the constructor:

final protected int nrColors;  final protected Map<Color, Color> successor = new HashMap<>();  final private Color first;    public ColorManager(int nrColors) {      this.nrColors = nrColors;      first = new Color();      Color previousColor = first;        for (int i = 1; i < nrColors; i++) {          final Color thisColor = new Color();          successor.put(previousColor, thisColor);          previousColor = thisColor;      }      successor.put(previousColor, Color.none);  }

We will use HashMap to keep the colors in an ordered list. At first, the choice of HashMap seems to be strange. ...