Testing equality of an enum value with equals is perfectly valid because an enum is an Object and every Java developer knows "==" should not be used to compare the content of an Object. At the same time, using "==" on enums:

For these reasons, use of "==" should be preferred to equals.

Noncompliant Code Example

public enum Fruit {
   APPLE, BANANA, GRAPE
}

public enum Cake {
  LEMON_TART, CHEESE_CAKE
}

public boolean isFruitGrape(Fruit candidateFruit) {
  return candidateFruit.equals(Fruit.GRAPE); // Noncompliant; this will raise an NPE if candidateFruit is NULL
}

public boolean isFruitGrape(Cake candidateFruit) {
  return candidateFruit.equals(Fruit.GRAPE); // Noncompliant; always returns false
}

Compliant Solution

public boolean isFruitGrape(Fruit candidateFruit) {
  return candidateFruit == Fruit.GRAPE; // Compliant; there is only one instance of Fruit.GRAPE - if candidateFruit is a GRAPE it will have the same reference as Fruit.GRAPE
}

public boolean isFruitGrape(Cake candidateFruit) {
  return candidateFruit == Fruit.GRAPE; // Compliant; compilation time failure
}

See