When all the elements in a Set are values from the same enum, the Set can be replaced with an EnumSet, which can be much more efficient than other sets because the underlying data structure is a simple bitmap.

Noncompliant Code Example

public class MyClass {

  public enum COLOR {
    RED, GREEN, BLUE, ORANGE;
  }

  public void doSomething() {
    Set<COLOR> warm = new HashSet<COLOR>();
    warm.add(COLOR.RED);
    warm.add(COLOR.ORANGE);
  }
}

Compliant Solution

public class MyClass {

  public enum COLOR {
    RED, GREEN, BLUE, ORANGE;
  }

  public void doSomething() {
    Set<COLOR> warm = EnumSet.of(COLOR.RED, COLOR.ORANGE);
  }
}