java - Java 中来自静态上下文的模糊调用

Question

main 方法尝试访问 var，但导致调用不明确。为什么？ Base1 中的实例变量 var 无论如何都无法从静态上下文访问(可见？)。

  class Base1 {
      int var;
  }

  interface Base2 {
      public static final int var = 0;
  }

  class Test extends Base1 implements Base2 { 
      public static void main(String args[]) {
          System.out.println("var:" + var); 
      }
  }

Answer 1

JLS rule for field access ambiguity是

If the identifier names several accessible (§6.6) member fields in type T, then the field access is ambiguous and a compile-time error occurs.

和on the subject of accessibility

A member (class, interface, field, or method) of a reference type, or a constructor of a class type, is accessible only if the type is accessible and the member or constructor is declared to permit access:

它不区分实例字段访问是否会在 static 上下文中导致编译错误。

注意你本来可以

public static void main(String args[]) {
    Test test = new Test();
    System.out.println("var:" + test.var); 
}

你仍然会有歧义。