[java] Initialize class fields in constructor or at declaration?

My rules:

  1. Don't initialize with the default values in declaration (null, false, 0, 0.0…).
  2. Prefer initialization in declaration if you don't have a constructor parameter that changes the value of the field.
  3. If the value of the field changes because of a constructor parameter put the initialization in the constructors.
  4. Be consistent in your practice (the most important rule).