Why Can't I Access a Protected Member in a Java Subclass From Another Package?

Understanding Java's protected Modifier

Problem:

Consider two classes, A and C, where C extends A. Suppose A declares an instance variable as protected int protectedInt = 1. Despite the expectation that protected members should be accessible within subclasses in other packages, Eclipse flags access to protectedInt in class C as not visible.

Answer:

The Java protected modifier allows access to a member within its own package and by subclasses, but only when the access is made through an instance of the subclass. This is because protected access is scoped to the subclass type, not to the class where the protected member is declared.

According to the Java Language Specification (JLS), "Access is permitted only within the body of a subclass S of C." This means that even though C extends A, the direct access of protectedInt from an instance of A is not permitted.

Solution:

To access protected members in a subclass, the subclass type must be used. For example, the following code would be valid:

C c = new C();
System.out.println(c.protectedInt);

In this case, the access is being made through an instance of the subclass (C), so the protected member is visible.

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