## Why is this an issue?

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);
      }
    }