Static Fields Prohibited in Inner Classes: Rationale

Java prohibits the declaration of static fields and methods within inner classes (or ordinary inner classes) due to their inherent instance-dependent nature.

Inner classes, unlike static nested classes, are tied to他們封閉班級的實例。這意味著內部類的每個實例都與封閉類的特定實例都有獨特的關聯。結果，允許在內部類中允許靜態字段在靜態字段所屬的實例中產生歧義。

此外，允許內部類中的靜態字段與基於實例的依賴關係的原理相矛盾。 Since inner classes rely on instances of the enclosing class, it doesn't make sense for them to have static features, which are designed to operate independently of any instance.

class OuterClass {
  class InnerClass {
    static int i = 100; // compile error
  }
}

Clarity and consistency:

遵守設計原理：